By this point, if you haven’t already squeezed and zested your lime, you will want to do that first, so once you begin making the custard, it will be a smooth process and you will not have to start and stop.
Tip: before squeezing any type of citrus fruit (lemons, limes, oranges, etc.), it helps to give it a few rolls on a hard surface. This will soften up the fruit, make it easier to squeeze and render more juice. If you do not desire pulp, be sure to strain the juice before you add it to your recipe.