Tomato Tofu Basil Spread

*enough for 2-3 sandwiches, keep stored in the fridge, stays good for 3-4 days

1 onion

1 tbsp olive oil for the pan

¼ cup tomato purée

1 block firm tofu (200g)

¼ tsp salt, or to taste

1 tbsp white wine vinegar or juice of ½ lemon

2 handfuls of fresh basil