Fill a stock pot with salted water and cook linguine according to package directions. Dice the onion and garlic then sauté in olive oil until golden brown. Dice tomatoes and add to the frying pan along with the basil, salt, pepper and red pepper flakes. Lower heat then add a splash of white wine and allow to simmer. Add a small amount of olive oil to a separate frying pan over medium heat then place the salmon fillet skin side down into the pan. Gently flip the salmon after a few minutes or when it is golden brown and has a nice crust. Allow to cook through (cook time depends on the size of the fillet.) Remove frying pan from heat and add slices of Havarti Cheese to cover entire fillet. Place in broiler until cheese is melted.
To plate, add a generous amount of pasta topped off with the tomato mixture followed by the salmon fillet. Top off with a squeeze of lemon and serve immediately.