01 -
Cut the bell peppers in half, remove seeds and white membranes, then slice into ¼ inch (6 mm) strips. Peel and thinly slice the onion. Peel and finely chop the garlic.
02 -
Heat olive oil in a skillet over medium-low heat. Add onions and cook gently for 5 minutes, stirring occasionally and breaking up the onion slices. Add garlic and cook for another 5 minutes until onions are soft and melting, avoiding any browning.
03 -
Add the sliced bell peppers, stir well and cook gently for 10 minutes. Pour in the tomato puree, half the salt, and black pepper. Stir well, cover, and simmer gently for 30-40 minutes, stirring occasionally.
04 -
Remove the lid and stir in the white wine vinegar and sugar. Simmer for another 10 minutes until the sauce thickens slightly and peppers are tender. Taste and adjust salt if needed. Serve warm or at room temperature.