Place pie on a baking sheet to make it easier to take in and out of the oven.
Adjust oven rack to middle position and preheat oven to 450 degrees F. Spray 9-inch pie plate with cooking spray. Press tortilla into pie plate and spray lightly with more cooking spray. Toss cooked breakfast sausage, chopped peppers, onions and 1 cup shredded cheese in a large bowl until combined. Spread filling over tortilla. Whisk together eggs, milk, flour, baking powder, salt and pepper in bowl until smooth. Slowly pour over filling in pie plate. Sprinkle with remaining 1 cup cheese and bake until surface is golden brown, about 20-25 minutes. Let cool 5 minutes. Cut into wedges and top with sour cream and green onions.