Bring a pot of water to boil and cook the pasta until al dente. Reserve 1 cup of the cooking water before draining.

In the meantime, heat a large skillet over medium heat and add the olive oil, garlic, red pepper flakes and capers. Cook until the garlic is fragrant, about 60 seconds, then add the tuna and stir to combine. Add a few tablespoons of the pasta cooking water to create a sauce, adding more as needed. Season to taste with salt, pepper, and the lemon zest and juice.

Add the cooked pasta and cherry tomatoes. Toss well to combine. Add the arugula and continue tossing, allowing it to wilt, and seasoning with salt, pepper and additional red pepper flakes as needed. Serve immediately.