Rinse the peppers, cut off the top and clean them from pulp and seeds. Pour the white wine and vinegar into a pot, add spices, herbs, and salt to taste, bring to a boil, and blanch the peppers for 3-4 minutes.
Remove them from the pot, place their opening downwards, and let them drain for 4-5 hours (or for the whole night).
Prepare the filling: drain the tuna and chop anchovies and capers coarsely. Put everything into a blender and chop until obtaining a smooth mixture.
Using a teaspoon, or a piping bag, put the filling into the peppers and gently place them into a sanitized glass jar, with the filling facing up.
Fill the jar with Olio Extravergine d’Oliva DOP Terre di Siena, close it, and proceed to create the vacuum. Sweet peppers stuffed with tuna and capers with Olio Extravergine d’Oliva DOP Terre di Siena are ready! Remember you can’t keep them for more than three months.