1 1/3 cups all purpose flour
3/4 teaspoon baking powder
1/2 cup sugar
1 cup (2 sticks) unsalted butter, at room temperature, plus more for greasing the pan
1 teaspoon salt
3/4 cup sweetened condensed milk
3 large eggs
1 teaspoon vanilla extract

Preheat oven to 325°F. Generously butter 9×5 loaf pan and set aside.
Stir the flour and baking powder together in a small bowl and set aside. Fit your food processor with the blade attachment and add the sugar, butter, and salt to the bowl. Process until light and fluffy, about 2 minutes, scraping down the sides and bottom of the bowl occasionally. Add the condensed milk and pulse until well incorporated, about 15 times, scraping down the sides of the bowl once. Add the sifted dry ingredients and pulse until no traces of flour remain, about 10 times. Add the eggs and vanilla, and pulse just until combined, about 5 times. Scrape down the sides and bottom of the bowl and finish mixing by hand to fully incorporate the eggs.
Transfer the batter to the prepared loaf pan. Bake until the top is dark, golden brown and a tester inserted in center comes out clean, about 1 hour. Cool in pan on a wire rack for ten minutes, then unmold and allow to cool completely on the rack, bottom-side down.