1cup (2 sticks) unsalted butter, at room temperature, plus more for pan
3cups sugar
6 large eggs
1 teaspoon baking soda
1cup sour milk or buttermilk
3cups all- purpose flour
1 teaspoon cream of tartar
Freshly squeezed lemon juice and zest (optional)
Instructions
Preheat the oven to 325°F and generously butter a 9-inch Bundt or angel cake pan.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs, one at a time, until the mixture is smooth. In a separate bowl, stir the baking soda into the sour milk. Sift together the flour and cream of tartar onto a sheet of wax paper or into another bowl. Add the flour mixture and sour milk alternately to the creamed mixture, starting and ending with the flour. Stir just until everything is combined. If you’d like, fold in a splash of lemon juice and a little zest, for brightness. Pour the batter into your prepared pan and smooth the top.
Bake until golden and a toothpick inserted into the center comes out clean—about an hour.
Remove from the oven and let the cake cool before slicing.