Preheat the oven to 325°F (165°C). Grease and flour a 9×5-inch loaf pan or a bundt pan. Set aside.
In a large mixing bowl, beat the softened butter and granulated sugar together using an electric mixer on medium speed until light and fluffy (about 3–5 minutes).
Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Combine dry ingredients: In a separate bowl, whisk together the flour, baking powder, and salt.
In another bowl, stir together the sour cream (or Greek yogurt), lemon zest, lemon juice, and vanilla bean seeds.
Gradually add the dry ingredients to the butter mixture in three additions, alternating with the sour cream mixture in two additions. Begin and end with the dry ingredients. Mix just until combined — do not overmix.
Pour into the prepared pan and smooth the top with a spatula. Place in the preheated oven and bake for 60–70 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for 10–15 minutes, then transfer to a wire rack to cool completely.
Once cooled, slice and enjoy! Optional: dust with powdered sugar or glaze with a lemon-vanilla icing.