In a bowl of a standing mixer fitted with the paddle attachment, beat butter, lemon zest, and sugar at medium speed until fluffy. About 5 minutes, stopping as scraping the sides of the bowl once in a while. Add eggs, one at a time beating well after each addition.
In a medium bowl, whisk together flour, salt, and baking powder. Gradually add flour mixture to butter egg mixture alternating with milk, beginning and ending with flour mixture. Beat well in between each addition.
Spray a 10-cup Bundt pan with baking spray with flour. Pour batter into prepared pan. Firmly tap pan on the counter to settle any bubbles that may have formed.
Bake until a toothpick is inserted and comes out clean, about 1 hour. Let cool in pan for 10 minutes. Remove from pan and let cool completely on a wire rack.