Keep drained oil.
Break up Tuna with fork and set aside.
In large skillet heat 1 tbls of the olive oil over medium heat.
Add garlic and cook, stirring for 30 seconds.
Add tomatoes with their juice and re pepper flakes.
Break up the tomatoes with a fork.
Simmer over low heat until slightly thickened, about 15 minutes.
Stir in Tonno and set aside.
Meanwhile, cook spaghetti in large pot of boiling water until al dente, 8-10 minutes.
Drain it and return to the pot.
Add the sauce and 3 tbls of parsley: toss to combine.
Taste and adjust seasonings.
Transfer to a serving bowl, sprinkle with the remaining 1 tbls parsley and serve immediately.