Preheat oven to 350°F. Line 18 wells of 2 cupcake tins with paper liners. Set aside.
Whisk the flour, salt, baking powder, and baking soda together in a medium-sized bowl. Set aside.
3½ cups all-purpose flour, 1½ teaspoons kosher salt, ½ teaspoon baking powder, ¼ teaspoon baking soda
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, sugar, and shortening together on high speed for 1-2 minutes, or until smooth, fluffy, and lighter in color.
1 cup salted butter, ⅔ cup granulated sugar, ⅓ cup vegetable shortening
Add the eggs and beat together for 30 seconds, or until fully incorporated. Scrape the sides down.
2 large eggs, 1 large egg yolk
Add in the remaining ingredients and beat together for 30-45 seconds or until completely combined. Add in the flour mixture and mix only until the flour has been incorporated.
11 tablespoons sour cream, 3 tablespoons fresh lemon juice, 1½ teaspoons pure vanilla extract, 2 tablespoons lemon zest
Divide the cupcake batter between the cupcake tins.
Place the cupcake pans into the oven to bake for 38 minutes, or until a toothpick inserted comes out clean or with moist crumbs. Once baked, remove from the oven and place onto a cooling rack to cool completely.