Ingredients

• 1 tablespoon extra-virgin olive oil (preferably Spanish)
• 1 medium yellow onion, thinly sliced
• 1/2 teaspoon sea salt, divided
• 4 plum tomatoes, halved lengthwise
• 1 baguette, cut into 16 slices (1/2 inch each) and toasted
• 1 can (6 ounces) Spanish oil-packed bonito tuna (such as Ortiz), drained and flaked
• 1 tablespoon chopped fresh chives

Instructions

1. Heat oil in a medium pan over low heat. Cook onion until golden brown, about 30 minutes. (Add 1 to 2 tablespoons water if onions stick.) Add 1/4 teaspoon sea salt; set aside. Place a grater over a bowl. Rub cut surfaces of tomatoes across grater. Discard skins. Add remaining ¼ tsp salt. Spread grated tomato over toasts (about 1 teaspoon per toast). Top with onion and tuna. Garnish with chives.