Pour 1 cup sugar and 2 Tbsp lemon zest into a large bowl or the bowl of a stand mixer. Use your fingertips to massage the zest into the sugar to help release the oil in the zest. You should be able to smell the oils being incorporated into the sugar.
Add 1/2 cup of room temperature butter into the sugar and mix on high with either an electric hand mixer or a stand mixer fitted with a whisk attachment. Cream together for about 3 minutes, until the mixture becomes lighter in color and looks fluffy. Scrape the sides and bottom of the bowl as needed with a rubber spatula.
Next, add 1 egg, 1 Tbsp lemon juice, 2 tsp lemon extract, and 1 tsp vanilla extract. If you want these cookies to have a yellow color, add in a small drop of yellow gel food coloring or 1/2 tsp of liquid yellow food coloring. Mix on a low speed until combined.
Sift 1 2/3 cups of flour, 1 tsp cornstarch, 1/2 tsp baking soda, 1/4 tsp baking powder, and 1/4 tsp fine salt into the wet ingredients. If you don't have a sifter, whisk the dry ingredients together in a separate bowl before adding them into the wet ingredients. This helps prevent over-mixing the dough and helps give these cookies a fluffy texture.
Mix the dry ingredients into the wet ingredients on a low speed until just combined.
Scoop the dough using a 1 1/2 Tbsp cookie scoop and roll into 20 balls. Place the cookie dough scoops on a parchment lined baking sheet or flat plate and chill in the fridge for 30 minutes.
While the cookie dough chills, preheat the oven to 375 F / 190 C and line two baking sheets with either parchment paper or silicone mats. I prefer using silicone baking mats.
Then add 1/2 cup powdered sugar in a small bowl. Remove the cookie dough from the fridge and roll the dough into a round ball. Toss each cookie in powdered sugar. Be sure to completely coat each cookie and aim to get a thick coating of sugar so that it will still be visible after baking.
Place the cookie dough on the lined baking sheets, spacing them about 2 inches apart.
Bake one tray at a time for about 12-13 minutes then place the tray of the cookies on a wire cooling rack. Bake time will vary if you make smaller or larger cookies, so keep an eye on them! The edges should look set, and the center should look slightly underbaked. The cookies will continue to bake as they cool on the pans.
Zest one more lemon over the top of the warm cookies to give them a nice, bright lemon flavor. Let the cookies cool fully on the baking pan, then enjoy! These cookies can be stored in an airtight container for up to 5 days.