Tuna pâté

Melt about 50 g butter in a small frying pan. Add onion, garlic and anchovy and stir over a low heat until onions are soft.
Do not allow mixture to brown. Remove from the heat and set aside to cool.
Meanwhile, melt 30-45 g of remaining butter in a frying pan and cook the tuna for about 3 minutes on each side until the tuna is medium rare (quite pink in the middle).
Transfer to a plate and allow to cool to room temperature.
Put tuna into a food processor with onion mixture and remaining ingredients, including remaining butter. Process to a smooth paste. Add salt and pepper and more lemon juice if needed.
Spoon mixture into a bowl, cover with plastic wrap and chill for about 40 minutes.
Serve with toast and capers.