Start by preheating your oven to 350°F (175°C). Then, grab your loaf pan and give it a good greasing with butter or some non-stick spray. To make sure nothing sticks, you can also sprinkle a little flour on top or line the pan with parchment paper. This helps your cake come out perfectly every time!

In a big bowl, use an electric mixer or a whisk to beat together the softened butter, peanut butter, and sugar. Keep going for about 3 to 5 minutes until the mix looks light, creamy, and fluffy—that’s when you know it’s just right.

Now, add your eggs one at a time, beating well after each one so everything blends smoothly. Then stir in the vanilla and milk (or sour cream) until the batter feels nice and combined.

In another bowl, whisk together your flour, baking powder, baking soda, and salt. Slowly add this dry mix to your wet ingredients, alternating with any extra milk if the batter seems too thick. Mix gently and just until everything comes together—you don’t want to overwork the batter.

Pour your batter into the prepared pan and smooth out the top with a spatula. Pop it into the oven for 45-50 minutes. To check if it’s done, stick a toothpick in the middle—if it comes out clean, you’re good! Let the cake cool in the pan for about 10 minutes before moving it to a wire rack to cool completely.