Spray an 8-inch baking dish with gluten-free nonstick cooking spray.
Cut or crumble the muffins into 1-inch pieces and put in the baking dish.
Whisk together the eggs, milk, and vanilla. Pour over the muffins in the baking dish. Press with a spatula to submerge the muffins in the liquid. Cover and refrigerate for 1 hour.
Preheat the oven to 350 degrees. Drizzle the melted butter over the bread pudding. Bake the bread pudding for 35 minutes or until the custard is fully set. Let cool slightly.
Puree the raspberries and strain through a fine sieve.
Dust the bread pudding with powdered sugar. Drizzle with the raspberry puree and serve.