Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking pan.

In a large bowl, combine the melted butter, granulated sugar, and brown sugar. Mix until smooth.

Add the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract.

In a separate bowl, whisk together the flour, baking powder, cinnamon, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Spread the batter evenly into the prepared baking pan.

In a small bowl, mix together the topping ingredients. Sprinkle evenly over the batter.

Bake for 25-30 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out clean.

Allow the bars to cool completely in the pan before cutting them into squares.