Quarter and core the peppers and place skin side up on a baking sheet. Roast the peppers on the top rack in the oven until the skin has black bubbles. Take out of the oven, cover with a damp tea towel and peel the peppers after 5 minutes. Alternatively, you can use roasted peppers from the jar.
Roughly chop the walnuts and roast them in a pan without fat. Cut the peppers into large pieces, puree with walnuts and tomato paste.
Stir in the olive oil and lemon juice. Season to taste with paprika powder, salt and pepper.