Boil pasta according to package. Set aside a few tablespoons of pasta water for later.
While the pasta cooks, heat olive oil in a pan on medium heat. Add in garlic and cook for 1 minute. Add onion and cook for 2 more minutes, or until the onion is translucent.
Pour in heavy cream and gochujang, stir to combine. Bring to sauce to a simmer and add in the pasta.
Reduce heat to low and add in tuna and parmesan. Season with salt & pepper. Stir until cheese is melted, slowly adding in reserved pasta until the sauce reaches desired consistency.
Serve with chopped green onion and more grated parmesan!