Peel and finely dice the onion and garlic.
Heat the oil in a pan and saute the onion and garlic until softened.
Pour in the wine and allow to bubble.
Dice the cheese.
Add to the pan and stir to melt.
Mix the cornflour with the stock and cream.
Pour into the cheese sauce, stirring, and simmer for 5 minutes until creamy. Season with salt and pepper and add some extra stock if needed.
Cook the tortellini in boiling salted water according to the pack instructions.
Wash the tomatoes, quarter, core and cut into small cubes.
Drain the tortellini and place on plates. Add the sauce and serve garnished with the tomato cubes.