• Preheat the oven to 350 degrees then spray a 9x13” baking pan with nonstick spray and set aside. Alternatively you can line the baking pan with parchment paper, allowing it to hang off the ends for easy removal of the bars from the pan.
• Add the softened butter and sugar to the bowl of an electric mixer, or to a large glass bowl if using a hand-held mixer, then beat on medium speed (6/10) until fluffy and pale yellow, 1 minute. Scrape down the sides of the bowl then add 1 egg and mix on low speed until just combined. Add the second egg then mix until just combined. Add the vanilla extract then mix until combined. Scrape down the sides of the bowl.
• In a separate bowl, whisk together the gluten free baking flour, baking powder, and salt. Add the dry ingredients to the wet ingredients in two batches, mixing on low speed until just combined before adding the next batch.
• Scoop the dough into the prepared baking pan then spread into an even layer with the spatula or an offset spatula — the dough will be sticky, and that’s ok. Bake for 20-24 minutes or until the tops and sides are light golden brown, rotating the baking pan halfway through. Avoid over-baking as we want the bars to be soft. Cool the bars completely.

For the Frosting:

• Add the softened butter to the bowl of an electric mixer, or to a large glass bowl if using a hand-held mixer, then beat on medium-high speed (8/10) until pale and creamy, 1 minute. Scrape down the sides of the bowl then add the powdered sugar, milk, vanilla extract, and salt. Mix on low until the powdered sugar is mostly wet then turn the speed up to medium (6/10) and beat for 2 minutes, scraping down the sides of the bowl halfway through. Add gel food coloring, if using, then beat to combine.
• Spread the frosting onto the cooled bars then top with sprinkles. I like to let the bars sit uncovered for an hour to give the frosting time to set on top before slicing into squares and serving. Store for up to 2-3 days covered on the countertop, or up to 5 days in the refrigerator.