Preheat your waffle iron while you make the batter.

In a large bowl, mix together flour, sugar, baking powder, cinnamon, and salt.

In a separate bowl, whisk together milk, eggs, and peanut butter until blended. Stir into dry mixture until well incorporated; a few lumps is OK.

When ready to cook, stir in the melted butter.

Lightly coat your waffle iron with nonstick spray if needed, and cook waffles according to manufacturer's instructions.

Serve immediately or let cool and freeze for later.