Preheat the oven to 350ºF (180°C).
Butter or spray a 9x5 inch loaf pan. You can line it with a strip of parchment paper, covering the pan's bottom and two long sides. The two short sides will remain unlined but greased. This will help you remove the cake from the pan.
Cream 1 cup butter in a large mixing bowl with an electric mixer or a stand mixer with the paddle attachment, gradually adding 1 cup sugar. Beat at medium speed until pale and fluffy, about 3 minutes.
Add 4 eggs, one at a time, beating well after each addition and scraping the sides of the bowl a few times. Don't worry if the mixture looks separated or curdled; it will come together when you add the flour.
Beat in 2 teaspoons vanilla extract.
Sift 2 ¼ cups all-purpose flour, ¾ teaspoon baking powder and ¼ teaspoon salt together and add them to the butter in three additions, alternating with ¼ cup sour cream in two additions, beginning and ending with flour.
Mix *just* until incorporated. Do not over mix. Use a spatula to give it a few stirs and check there’s no flour spots. Scrape the batter into the prepared pan and even out the top.
Bake for 45-50 minutes, or until a cake tester or toothpick inserted in the center comes out clean. It should spring back if you lightly touch it.
Transfer to a wire rack and let cool for 20 minutes or so.
Run a smooth-bladed knife around the pan's edge to ensure the cake is not sticking. Remove the cake by lifting the ends of the parchment paper. Remove the strip of paper and let the cake cool completely on a cooling rack.
This cake lasts up to 3 days at room temperature, well covered in plastic wrap, foil, or in an airtight container.