In a little bowl, squeeze out juice from the lemon and mix with baking soda. It will foam. Add to the eggs and sugar.
½ lemon,, ½ tsp baking soda
Add sour cream and vanilla to the mix. Beat all together.
2 cups sour cream, 1 tsp vanilla extract
On low speed, mix in the flour.
3 cups flour,
The dough will be a bit sticky. Transfer into a bowl, cover, and put in the freezer for 1 hour.
After an hour take the dough out. Preheat your oven to 350 F. Prepare 2 baking sheets with parchment paper (you can also just spray with oil).
Wet your hands, this will help you roll the batter into balls easily. Make balls and place them on cookie sheets. Leave room between each ball.
Bake for 20 minutes or until the bottom of the cookies start to get a brownish color.
While the cookies are baking, make the vanilla glaze recipe: Beat the egg whites for 1 minute with a hand mixer. Then add powdered sugar and beat until well incorporated.
2 egg whites, 2½ cups powdered sugar
When you take out pryaniki from the oven, let them cool down for a few minutes. Brush the glaze all around each cookie. (The glaze will dry fast on the cookies, so brush the tops, let dry, then flip over and glaze the bottoms.)
Store either in a ziploc bag or in a covered dish.
Notes
Make sure to let the cookie batter sit in the freezer before forming into cookies and baking.