Preheat the oven to 325 (F). Prepare your loaf pan by generously buttering or spraying with cooking spray.
In a medium bowl, whisk together 1 1/3 cups flour, 3/4 teaspoon baking powder, and 1/2 teaspoon salt. Set aside.
In the bowl of a freestanding electric mixer with a paddle attachment, cream together 1 cup unsalted butter and 1/2 cup granulated sugar on medium-high speed, until light and fluffy.
Once the butter and sugar is light and fluffy, turn the mixer to its lowest speed and slowly add 3 eggs, one at a time, only adding each egg after the egg before it has been fully incorporated.
Once the eggs have been incorporated, turn off the mixer and whisk together 2 teaspoons vanilla extract and 3/4 cup sweetened condensed milk.
Turn on the mixer to its slowest speed and add the dry ingredients (from the second step) in 3 parts, alternating with the sweetened condensed milk mixture (from the fourth step) in two parts. DO NOT OVERBEAT — simply beat together until all the ingredients have just been incorporated.
Transfer to your prepared loaf pan, using a rubber spatula to spread the batter evenly across the pan. Bake in the preheated oven for about 1 hour, or until the top is a dark, golden brown and a skewer inserted into the middle of the cake comes out clean. Cool completely on a wire rack before unmolding.