In a small bowl, warm the milk to about 110째F (43째C).
Add 1 tablespoon of sugar and the yeast to the warm milk. Stir and let it sit for about 10 minutes, or until frothy.
In a large mixing bowl, combine the flour, remaining sugar, and salt.
Add the melted butter, eggs, vanilla extract, lemon zest (if using), and the yeast mixture.
Mix until a dough forms, then knead the dough on a lightly floured surface for about 10 minutes, or until smooth and elastic.
If using raisins, knead them into the dough until evenly distributed.
Place the dough in a greased bowl, cover with a clean cloth, and let it rise in a warm place for about 1-2 hours, or until doubled in size.
Punch down the risen dough and divide it into two equal parts.
Shape each part into a round loaf and place them in greased round baking pans.
Cover and let the dough rise again for about 30-45 minutes, or until doubled in size.
Preheat your oven to 350째F (175째C).
Brush the tops of the loaves with the beaten egg.
Bake for about 30-40 minutes, or until the loaves are golden brown and sound hollow when tapped on the bottom.
Remove the paska from the oven and let them cool on a wire rack.
Slice and serve.
Enjoy your meal!