Thinly slice the onion and sauté until golden in a large skillet with a drizzle of olive oil.
Break the sausages into pieces and brown them for 3 to 4 minutes.
Deglaze with a glass of white wine and allow the alcohol to evaporate.
Add the tomato passata.
Season with a pinch of salt and cook over low heat for 10 to 15 minutes until the sauce has thickened.
Prepare the polenta according to standard method (bring water to a boil with salt and olive oil, then slowly whisk in the polenta flour until cooked).
To serve, ladle a portion of polenta onto each plate, add one or two sausages along with plenty of sauce, and garnish with grated Pecorino or Parmesan cheese to taste.