Cook fettuccine according to package instructions; drain and set aside.
In a large skillet, melt butter and sauté garlic, jalapeños, and red onion until fragrant.
Add chicken and cook until lightly browned, then toss in bell peppers.
Pour in tequila, lime juice, soy sauce, and chicken stock; simmer for a few minutes.
Stir in heavy cream and chopped cilantro, cooking until the sauce thickens.
Add the cooked fettuccine, tossing well to coat in the creamy sauce.
Cook for another 2 minutes until everything is well combined.
Serve hot, garnished with extra cilantro if desired.