Ingredients

2 1/4 cups all-purpose flour 

2 teaspoons cream of tartar 

1 teaspoon baking soda 

1/2 teaspoon salt 

12 tablespoons (1 1/2 sticks) unsalted butter, softened 

1/4 cup vegetable shortening 

1 1/2 cups granulated sugar 

2 large eggs 

2 tablespoons freshly grated lemon zest 

Colored sanding sugar, for rolling 

Preparation

Preheat oven to 400 degrees. Line baking sheets with parchment paper; set aside. Whisk together flour, cream of tartar, baking soda, and salt in a medium bowl. Cream butter, shortening, and granulated sugar on medium-high speed in the bowl of a mixer with the paddle until pale and fluffy, about 3 minutes. Mix in eggs and zest. Mix in flour mixture, scraping down sides of bowl as needed. Refrigerate dough 15 minutes.

Roll teaspoonfuls of dough into balls; roll in colored sugar. Place 2 inches apart on lined sheets. Bake until edges are set but centers are soft, 7 to 8 minutes. Cool on sheets 2 minutes; transfer to wire racks.