Heat 1 tablespoon olive oil to non-stick skillet; add onions and peppers and saute’ until onions are slightly translucent, stirring occasionally (about 3 minutes; don’t over-cook – you want the onions and peppers to be a little crunchy).
In a separate small skillet, break sausage into chunks and saute’ until no longer pink.
Place flatbread on a baking sheet and sprinkle on remaining 2 tablespoons of olive oil, spreading with a pastry brush.
Using a large spatula or pizza peel, transfer flatbread directly to hot oven racks (not on baking sheet) and bake for 3 minutes.
Using a large spatula or pizza peel, remove flatbread from oven to baking sheet.
Sprinkle mozzarella cheese evenly over flatbread, followed by Parmesan cheese.
Add onions, peppers and sausage to flatbread.
Return to oven (on baking sheet) and bake 8 minutes more until edges are lightly browned.
Remove from oven and transfer to cutting board; cut into 6 to 8 pieces.
Serve immediately.
Notes
Cooking time includes cooking onions, peppers and sausage.