Prep the vegetables: Slice the zucchini into half-moons, about 1/4 inch thick.
Dice the onion. Mince the garlic. Halve the cherry tomatoes.
Zest and juice the lemon.
Heat the pan: Warm 2 tablespoons of olive oil in a large skillet over medium heat. Add the onion with a pinch of salt and cook 3–4 minutes until softened.
Sauté the zucchini: Add the zucchini and another drizzle of oil if the pan looks dry. Cook 5–7 minutes, stirring occasionally, until lightly browned and tender with a slight bite.
Add aromatics: Stir in the garlic, dried oregano, and a pinch of red pepper flakes.
Cook 30–60 seconds until fragrant.
Toss in tomatoes and capers: Add the cherry tomatoes and capers. Cook 2–3 minutes, just until the tomatoes begin to slump and release a little juice.
Fold in the tuna: Drain the tuna well. Flake it gently into the skillet.
Stir carefully to combine without breaking it up too much. Warm through for 1–2 minutes.
Finish bright: Add lemon zest and 1–2 tablespoons of lemon juice. Season with salt and black pepper to taste.
Remove from heat.
Herbs and cheese: Fold in chopped parsley or basil. If you like, sprinkle with a little grated Parmesan or crumbled feta for richness.
Serve: Enjoy straight from the skillet, or spoon over rice, quinoa, or pasta. It’s also great piled onto toasted bread or wrapped in a warm pita.