Heat the oil in a large skillet over medium-high heat. Add the peppers and onions and sauté with a generous pinch of salt over medium heat until tender, 7-8 minutes. Reduce the heat to medium-low, add the butter and stir until melted.
In the meantime, cook the ravioli according to package instructions and drain, reserving ½ cup of the pasta cooking water. Add the ravioli to the pan and toss gently to incorporate, then add the cheese and toss again, adding the reserved pasta cooking water a little at a time to acheive a sauce-like consistency. Season with salt and pepper to taste.
Divide the pasta among plates and garnish with more cheese, if desired.