Start by browning your butter. Melt it in a sauce pan over medium heat and stir constantly until it smells nutty and stops sizzling, about 5-8 minutes. Set this aside and let it cool.
½ Cup Butter
Preheat your oven to 350℉. Line your baking dish with parchment paper, leaving some overhang for easy removal later.
In a bowl, whisk together your flour, baking powder, cinnamon, and nutmeg.
1¼ Cups Flour, ½ Tsp Baking Powder, ½ Tsp Cinnamon, ¼ Tsp Nutmeg
In another bowl, beat the brown butter and brown sugar until well combined. Add the egg and vanilla to this mix and combine them.
1 Cup Brown Sugar, 1 Tsp Vanilla Extract, 1 Egg
Add the flour mix to the butter-sugar mix and stir it until it's mostly combined. Don't worry about small bits of flour, but get the big lumps out.
Add the apples and fold to mix together, which finishes mixing any stray flour.
1½ Cups Diced Apples
Transfer your batter to your baking dish, spreading it out flat and even. It'll be thick, almost like a cookie dough; that's fine.
Bake your blondies for 30 minutes, testing near the end to reach the consistency you prefer.
When done, remove from the oven and let cool for at least 30 minutes. Top with ice cream, whipped cream, or more apples, and enjoy!