Preheat the oven to 350°F (175°C). Line a 9-inch square baking dish with parchment paper.

In a large mixing bowl, combine brown sugar, melted butter, eggs, and vanilla extract until smooth.

Add flour, baking powder, baking soda, and salt. Stir until fully incorporated.

Fold in the pastel M&M’s, reserving ¼ cup to sprinkle on top.

Press the dough evenly into the prepared baking dish.

Bake for 35-40 minutes, or until the edges are golden brown and the center is set.

Remove from the oven and allow to cool completely before cutting into 16 bars.