A thin, sharp lemon curd tart. The curd is cooked on the stovetop to a nappe and enriched with butter, then poured into a blind-baked tart shell and given a short set-bake. Where the lemon tart pours a raw custard into a deep shell and bakes it low and slow, this cooks the filling first — so it goes in thin, sets without curdling, and needs only minutes in the oven. Finished bare, no meringue.

Ingredients

   
1 batch tart shell — blind-baked and cooled (see step 1)
  Lemon curd
3 eggs (~150g)
1 egg yolk
130g caster sugar
3 lemons, zested
110g lemon juice (from the 3 lemons)
90g unsalted butter, cold, cubed
1 pinch salt

Steps

  1. Blind-bake the shell: roll the tart shell dough thin — 3mm, or a touch thinner for a crisper base — line an 8- or 9-inch pan, and bake fully per its recipe (350°F, 15 minutes with weights, then 5–8 minutes uncovered until golden and dry). Cool completely.

  2. Rub the lemon zest into the sugar with your fingertips until damp and fragrant — this pulls the oils out of the zest and into the curd.

  3. In a medium saucepan off the heat, whisk the eggs, yolk, lemon sugar, lemon juice, and salt until smooth.

  4. Cook over medium-low heat, whisking constantly, until it thickens to a nappe — it coats the back of a spoon and holds a line when you draw a finger through it, about 170°F. Do not let it boil. 6–8 minutes.

  5. Off the heat, whisk in the cold butter a few cubes at a time until the curd is smooth and glossy. If it looks at all grainy, pass it through a fine sieve.

  6. Pour the warm curd into the cooled shell in a thin, even layer and smooth the top.

  7. Set-bake at 350°F for 10–15 minutes, until the edges are set and the center only barely jiggles. It firms as it cools.

  8. Cool to room temperature, then refrigerate at least 2 hours to set. Serve plain, or dust with confectioners’ sugar or scatter fine candied zest just before serving.

Analysis

Total curd: 500g

Component Amount %
Liquid (egg water, lemon juice, butter water) 238g 47.6%
Sugar (added + lemon solids) 139g 27.8%
Fat (butter, egg) 95g 19.0%
Egg/protein 23g 4.6%
Inert (zest, salt) 5g 1.0%

The one number that separates this from the lemon tart is the 19.0% fat — and it’s almost all added butter. That tart’s raw filling carries 12.2% fat and 53% liquid, sets purely by egg protein, and so has to bake low and long (250°F, 30–45 minutes) to coagulate a thick, wet custard without curdling. This one does its coagulating first, on the stovetop: cooked to a nappe at ~170°F while whisked constantly, with 27.8% sugar and lemon acid both raising the temperature at which the eggs would scramble, the curd thickens into a set cream before it ever meets the shell. So the oven’s job shrinks to a 10–15 minute set-bake — enough to firm the surface and marry the curd to the pastry, not to cook it from raw. The butter, whisked in off the heat so it emulsifies rather than melts to oil, is what enriches the curd and, on chilling, firms it into a sliceable layer. It is not the plush Pierre Hermé crème au citron, which carries roughly double the butter and never bakes at all — this is the lighter, brighter, thinner baked-curd form.

Notes

  • This is the thin, sharp counterpart to the lemon tart. That one is a deep, dense baked custard set with cream; this is a thin layer of stovetop curd, brighter and more acidic, enriched with butter instead of cream. 500g of curd is a thin layer in a 9-inch shell or a slightly deeper one in an 8-inch. For a fuller tart, scale the curd up by half.
  • Cook to a nappe, not a boil. Constant whisking plus the sugar and acid keep the eggs from scrambling at 170°F; a boil will curdle them. If it does break, straining in step 5 rescues most of it — but pull it off the heat the moment it holds a line.
  • Butter goes in off the heat. Added below a boil, cold, a few cubes at a time, it emulsifies into the curd and gives it gloss and body. Melted into a hot boiling curd it just thins to oil.
  • The set-bake is optional. A fully cooked curd will set in the fridge on its own, so you can skip step 7 and simply chill — you’ll get a glossier, softer top. The short bake firms the surface to a matte set and fuses the curd to the shell for a cleaner slice; it does not cook the curd further. Either way, do not bake it long or hot, or the surface cracks.
  • Blind-bake the shell fully and let it cool. Unlike the lemon tart, the shell here gets no long bake with the filling to dry it out, so it must be crisp and cool before the curd goes in. A cooled curd is far less wet than a raw custard, so sogginess is a small risk — but a pale, underbaked shell will still soften.
  • For the richest version, make a lemon cream instead. Pierre Hermé’s crème au citron cooks a similar base to ~180°F, cools it to ~140°F, then blends in roughly double the butter (about 300g) with an immersion blender for 3 minutes to a silky emulsion — poured into the shell and only chilled, never baked. Plusher and thicker; a different tart.
  • No meringue. A bare lemon curd tart is the classic French form; meringue on top makes it a lemon meringue pie, a different dessert. Finish it plain, or with confectioners’ sugar, candied zest, or a few berries on the plate.
  • Lemons. Three lemons give both the zest and roughly the 110g of juice; zest before you juice. Grate only the yellow, not the white pith beneath, which is bitter.
  • Make-ahead and storage. The curd itself keeps a week refrigerated, so it can be made days ahead and the tart assembled to order. Assembled, the tart keeps 2–3 days refrigerated; cut with a hot, dry knife.