Step 1

In a large skillet or straight-sided sauté pan, combine oil and garlic. Cook over medium heat, turning garlic cloves occasionally, until garlic is deep golden brown on all sides, about 5 minutes. Using tongs or a slotted spoon, remove garlic from skillet; discard garlic. Add red pepper flakes and continue to cook, stirring constantly, until fragrant, about 30 seconds.

Step 2

Add tomatoes, season lightly with salt, and bring to a simmer. Cook, stirring occasionally, until oil is emulsified and sauce is thickened slightly, about 10 minutes. Reduce heat to medium-low, add fish sauce (if using) and tuna, and stir gently until just incorporated into sauce, taking care to keep pieces of tuna as intact as possible.

Step 3

Meanwhile, in a pot of salted boiling water, cook pasta until just shy of al dente (about 2 minutes less than the package directs). Using tongs, transfer pasta to sauce, along with 1/4 cup (60ml) pasta cooking water. Alternatively, drain pasta using a colander or fine-mesh strainer, making sure to reserve at least 1 cup (240ml) pasta cooking water.

Step 4

Increase heat to high and cook, stirring and tossing rapidly, until pasta is al dente and sauce is thickened and coats noodles, 1 to 2 minutes, adding more pasta cooking water in 1/4 cup (60ml) increments as needed to adjust consistency of sauce. Remove from heat, add parsley, and stir to combine. Season with salt to taste. Serve immediately.