Preheat your oven to 350°F (175°C) and grease a 9-inch round cake pan.

In a medium mixing bowl, combine flour, baking powder, baking soda, salt, black pepper, and garlic powder.

In a large bowl, beat together softened butter and granulated sugar until light and fluffy.

Add eggs one at a time and mix well, then add vanilla extract.

Gradually mix in the dry ingredients until just combined.

Fold in grated zucchini, carrots, diced bell pepper, and sour cream.

Pour the batter into the prepared cake pan, smoothing the top.

Bake for 30-35 minutes or until a toothpick comes out clean.

Let cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

Slice into wedges and serve warm or at room temperature.