1 teaspoon active dry yeast
Pinch of sugar
1/4 cup warm water
1 cup flour
1/2 teaspoon salt
1/2 teaspoon lemon zest (optional)
1 large egg, at room temperature
3 tablespoons unsalted butter softened
Dissolve the yeast and sugar in the water and let stand as you prepare the rest of the ingredients. Combine 1 cup flour, salt and lemon zest in a bowl, and whisk to incorporate. Make a well in the middle and add the egg and butter as well as the yeast.
With a wooden spoon, mix until you get a soft, stickyish dough. Dust with flour and transfer the dough to a clean bowl. Cover the bowl and let the dough rise for about 45 minutes to 1 hour, until doubled in size. You can either shape the dough at this point, or knead it down and give it an additional rise.
Butter a 9 inch tart pan with a removable bottom.
Knead the dough down again and place it in the center of your pan. Press the dough out to the edges of the pan. The dough should be thicker on the sides than in the center. If it snaps back as you try to spread it, just let it rest for a few moments before trying again. Fill and bake in the middle of a 375 oven for 35 to 45 minutes.