1.In a large saucepan, heat oil on high. Saute onion 1-2 minutes until tender.
2.Stir in cherry tomatoes and parsley. Cook 1 minute. Mix in tuna with oil and lemon juice. Season to taste.
3.In a large saucepan of boiling, salted water, meanwhile, cook fettuccine following packet instructions. Drain and return to pan.
4.Toss tuna mixture through the hot pasta. Serve topped with parmesan.
To make a simple pesto, pound 2 garlic cloves with a good pinch of salt in a mortar. Add 2 tablespoons pine nuts and a bunch picked basil leaves, pounding until a creamy paste forms. Blend in ⅓ cup olive oil and 2 tablespoons grated parmesan. Season with black pepper to taste.