Lemon Tart
A baked lemon curd set entirely by egg, in a blind-baked shell, with no starch thickener at all.
What's going on here
Unlike pastry cream, this filling sets by egg protein coagulation alone, with no starch involved, which puts it under a much narrower temperature window. Starch-thickened custards are deliberately pushed to a full boil, since the starch protects the eggs from curdling even at that heat; a filling with no starch has no such protection, and egg proteins that overheat curdle outright, turning a smooth curd into a grainy, weeping mess with visible small curds throughout. So this tart bakes at a distinctly low oven temperature and is pulled the moment the centre still jiggles like a not-quite-set jelly — residual heat finishes the coagulation as it cools, the same principle as a baked cheesecake, but with a far smaller margin, since there's no starch buffering the eggs from the oven's heat at any point.
Ingredients
Shell
- 1Sweet tart shell, blind-baked
see the Sweet Tart Shell recipe — bake it slightly less than fully, since it goes back in the oven
Filling
- 4Eggs
- 1 cupGranulated sugar
- 1 tbspLemon zest
- 2/3 cupLemon juice
from about 4 lemons
- 1/3 cupButter, melted
Instructions
Prep
- Heat the oven to 150°C (300°F).
Tip: Noticeably lower than most bakes in this book — a starch-free egg filling has almost no margin against overheating.
Filling
- Whisk the eggs and sugar together until smooth, then whisk in the lemon zest, lemon juice, and melted butter until fully combined.
- Strain through a fine sieve into a jug to catch the zest and any bits of cooked egg white from the whisking.
Tip: Straining is what gives this the smooth, glassy set a good lemon tart is known for.
Bake
- Pour into the blind-baked shell and bake until the edges are set but the centre still jiggles like a not-quite-set jelly when the pan is nudged.
Tip: Pull it looking underdone. It firms up entirely as it cools — a filling that looks fully set in the oven has already gone past the point of a smooth curd.
Cool
- Cool completely at room temperature, then chill before slicing.
Claude Score
Well-built recipe. Sound ratios and real flavor development.
- Ratio soundness25% of total
- 88
- Flavor development25% of total
- 90
- Texture control20% of total
- 86
- Reliability20% of total
- 74
- Pantry accessibility10% of total
- 86
How well the formula holds up against known working ratios.
Whether the method builds flavor or merely combines ingredients.
How deliberately moisture, gluten, starch, and fat are controlled.
How much margin for error the recipe leaves a home cook.
Whether you can make it from staples, right now, with normal gear.
Correctly identifies why this filling behaves so differently from a starch-thickened one, and is honest about the narrow doneness window that follows from having no starch buffer.
Scored on the science of cooking — ratios, flavour development, texture control, how forgiving the method is, and whether you can make it from what's in the cupboard. Not a measure of how much you'll like it.
Tips for this recipe
Filling turned grainy
Overbaked. Without starch to buffer them, the eggs curdled once they passed their setting point. There's no fixing a baked batch, but next time pull it earlier — trust the jiggle test over the clock.
Fresh lemon juice only
Bottled juice lacks the aromatic oils the zest brings and tends to taste flatter and more purely sour — worth juicing the lemons you zested rather than reaching for a bottle.