When there are about 10 minutes left on your crust timer, start making the custard.
Whisk together the sugar, eggs, yolks, salt, and zest in a 4-quart saucepan with a heavy bottom.
Once well combined, whisk in the lemon juice.
Turn the heat on low and heat, stirring gently, until just warm to the touch (3–4 minutes)
Increase the heat to medium-low and start temping with your Thermapen ONE as you continue to stir, scraping the bottom of the pot. When the custard reaches 170°F (77°C), after 8–9 minutes, remove it from heat.
The crust should have come out of the oven by now, so strain the custard right onto the crust.