1. Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius). Spray a Bundt pan with baking spray. Set aside.
2. In the bowl of an electric mixer on medium speed, beat together peanut butter, brown sugar, eggs, vanilla, salt, baking soda, and baking powder until combined.
3. Reduce mixer speed to low. Add half the flour, followed by half the milk, then the remaining flour and remaining milk. Mix until combined.
4. Pour batter into prepared Bundt pan. Bake for about 50 minutes, until the top feels firm. Set aside to cool completely before glazing.