First roast the spring onions wrapped in aluminium foil with coarse salt and oil, place in a frying pan over a medium heat or in the oven in an oven dish with a little water at 150ºC for 10 minutes. After that time, check if they are tender. On a long dish, place a base of Romesco sauce, then put spring onions on top and the slices of tuna belly accompanying the spring onions.
Finish with a few leaves of lemon thyme, chopped chives and the oil from the preserves.
Note: Romesco is a tomato-based sauce with almonds, peppers, paprika, bread, oil and vinegar.