On a medium/high heat, warm the olive oil in a large non-stick frying pan and cook the chopped onions until soft and golden. Add the chopped chorizo to the frying pan and cook for one minute before adding the drained tin of tuna. Stir together and add the balsamic vinegar along with half the garlic powder. Add all other ingredients to the frying pan and stir well. Fry for 5 minutes, or until the tomato sauce looks thick. (Be sure to taste if there is enough herbs/salt to your liking)
Bring a saucepan of boiling water to the boil and add the tagliatelle. Drain.
Add the tomato tuna sauce to the pasta, mix well and serve.