Heat oven to 350 F.
Roughly chop prosciutto.
In a medium skillet, heat olive oil; cook prosciutto, garlic and onions until onions are soft and golden-brown.
Add tomatoes and cook until liquid evaporates and sauce thickens, about 15-20 minutes.
Drain and place in a bowl with the olive oil, lemon juice, salt and pepper. Toss well to combine.
Place artichokes in a 1 ½ to 2-quart gratin pan. Top with tomato sauce and sprinkle with grated cheese.
Bake 15-20 minutes, until sauce thickens and cheese has melted.
Tip: This dish can be made in advance and reheated.