In a medium heatproof bowl, whisk together eggs and sugar until pale and slightly thickened—about 1 minute of elbow grease.

Stir in fresh lemon juice and zest, folding gently so the mixture glows bright yellow.

Place the bowl over a pot of simmering water—make sure the bottom doesn’t touch the water to avoid curdling.

Using a silicone spatula, whisk the mixture continuously, scraping the edges to prevent scorching.

Clip a candy thermometer to the bowl’s side; once it hits about 170°F (about 8–10 minutes), you’ll see the curd coat the spatula in a thick ribbon.

Remove from heat and stir in cubed butter, one piece at a time; it melts into a glossy, creamy curd.

Whisk in vanilla extract and a pinch of salt, tasting to tweak sweetness.

Pass the curd through a fine-mesh sieve to catch any stray zest or cooked egg bits, then pour into a clean jar.

Let your lemon curd cool to room temperature before sealing. Then refrigerate for at least 1 hour so it firms up to that perfect breakfast topping consistency.