Boil the Spaghetti: Fill a large pot with salted water and boil. Cook the spaghetti until al dente, about 8-10 minutes. Reserve a cup of pasta water, drain and drizzle with olive oil to keep warm.

Cook the Chicken: Heat olive oil in a skillet, season chicken with salt and pepper, and cook for 5-7 minutes on each side until golden brown. Slice chicken into strips.

Sauté Onion and Garlic: In the same skillet, reduce heat to medium-low, add diced onion and sauté until soft. Add minced garlic and cook until fragrant.

Create the Sauce: Pour in the chicken broth and bring to a gentle simmer. Stir in heavy cream and Monterey Jack cheese until melted and creamy.

Add Vegetables: Add halved cherry tomatoes and spinach, cooking until spinach wilts and tomatoes soften.

Combine Chicken and Spaghetti: Return chicken to skillet and add cooked spaghetti with a splash of reserved pasta water. Toss until well-combined.

Season and Serve: Taste and adjust seasoning. Serve garnished with Parmesan cheese and parsley or cilantro.