Nutrition per serving may change if servings are adjusted.
2½ teaspoons extra-virgin olive oil, divided
2 onions, thinly sliced
½ teaspoon salt, divided
½ cup chopped fresh, or drained canned tomatoes
Freshly ground pepper to taste
3 large eggs
2 large egg whites
1 6-ounce can chunk light tuna in water, drained and flaked (see Note)
Heat 1½ teaspoons oil in a medium nonstick skillet over medium-low heat. Add onions and ¼ teaspoon salt. Cook, stirring often, until very tender and starting to turn light golden, 10 to 20 minutes. (Add 1 to 2 tablespoons water, if onions are browning too quickly.) Add tomatoes and cook, stirring occasionally, until tomatoes have melted into the onions, about 10 minutes. Season with pepper; set aside to cool.
Whisk together eggs, egg whites and remaining ¼ teaspoon salt in a bowl. Fold in tuna and reserved onion mixture with a rubber spatula.
Wash pan, wipe dry and brush with remaining 1 teaspoon oil. Place over low heat. Add the egg mixture and stir gently to distribute tuna and onions. Cook over low heat until underside is golden and top is starting to set, about 5 minutes.
Use a spatula to loosen tortilla, then slide it onto a plate. Invert it back into the pan and cook until the bottom is set, about 1 minute. Slide onto a serving platter and cut into wedges. Serve hot or at room temperature.
Alternative Cooking Method
If flipping a large tortilla makes you nervous, finish the tortilla by placing the skillet under the broiler until the top is set and golden brown, about 2 minutes. Slide the finished tortilla onto a platter and serve.
Note: Chunk light tuna, which comes from the smaller skipjack or yellowfin, has less mercury than canned white albacore tuna. The FDA/EPA advises that women who are or might become pregnant, nursing mothers and young children consume no more than 6 ounces of albacore a week; up to 12 ounces of canned light tuna is considered safe.
136 calories;7.0 g fat(2.0 g sat); 1.0 g fiber; 7.0 g carbohydrates; 11.0 g protein; 30.0 mcg folate; 147 mg cholesterol; 4.0 g sugars; 0.0 g added sugars; 403.0 IU vitamin A; 9.0 mg vitamin C; 44.0 mg calcium; 1.0 mg iron; 497 mg sodium; 197.0 mg potassium