Prepare the ingredients. Wash the jalapeños and cut them in half.

Remove the veins and seeds. Heat 2 or 3 cups of water (480-720 ml) and dissolve the tablespoon of coarse salt. Add the jalapeños and let them cook just until they change color—be careful not to overcook; they should stay crisp.

Place the jalapeños in a strainer to drain well. Finely chop the remaining ingredients. Heat the olive oil in a large skillet. Sauté the onion.

Add the tomato and cook until it softens and changes color. Add the tuna and break it up well.

Add the olives, capers, and a pinch of oregano. Season with salt and pepper to taste. Fill the jalapeños with this mixture. Serve warm or cold. Enjoy with rice or a salad.