Combine eggs, milk, flour, salt, cinnamon, and vanilla in a blender and pulse until evenly combined and smooth. Let batter rest for 30 minutes at room temperature or up to overnight in the fridge.
When ready to bake, preheat oven to 425 degrees F.
Cut the butter into pats and arrange in a 9×13 inch baking dish, then add blueberries and place in oven for about 2-3 minutes, or until butter melts.
Pour the batter over the melted butter and berries and immediately return to the oven. Bake for 22 minutes or until edges have puffed up and started to turn brown.
Cut into slices to serve and top with powdered sugar, syrup, or whipped cream.
