Heat a deep-sided skillet or pan over high heat. Add 1 tablespoon of olive oil. Once the oil is hot, carefully add the lobster tails to the pan.
Add garlic cloves, salt, pepper, and red pepper flakes. Cover and cook for four minutes. Add 3 tablespoons of butter to the pan. Turn the lobster tails over, then pour in the wine and cook for 4 more minutes.
Meanwhile, place the shrimp in a large mixing bowl and toss with 1 tablespoon olive oil. Add blackened seasoning and toss to coat. Heat another skillet over medium-high heat. Add 1 tablespoon of butter. Once melted add the shrimp. Cook 3 minutes per side and then remove from heat.
Remove lobster tails from the pan and place them onto a wooden cutting board. Keep liquid in the pan as this will be used for the lobster sauce. Remove the shells and discard them. Roughly chop the lobster meat.
Add the heavy whipping cream, chicken broth, tomatoes, and onion to the same pan the lobsters cooked in. Lower the heat to medium-low and simmer the sauce for 4 minutes. Stir in the lobster meat and shrimp and cook for 2 more minutes.
While the sauce is cooking, bring a large pot of salted water to a boil. Cook the fettuccine according to package directions until al dente.
Combine the lobster sauce and fettuccine. Add the green onions and stir. Garnish with parsley and parmesan before serving warm.