Meanwhile, in large high-sided skillet, heat oil over medium; once shimmering, add garlic and sauté until fragrant, 30 seconds to 1 minute. Stir in oregano, cumin, and lemon zest and cook for a few seconds longer. Add cherry tomatoes and cook, stirring often, until easily burst when pressed gently with wooden spoon, 8 to 10 minutes. Stir in corn, tuna or salmon, and lemon juice.