Bring a large saucepan of water to a boil and cook pasta according to package instructions. Drain and set aside.
While pasta is cooking, heat olive oil in a large skillet over medium heat and add chicken in an even layer. Season evenly with a pinch of salt and pepper. Cook for 4-5 minutes on one side, flip and cook for additional 3-5 minutes, stirring frequently until cooked through. Remove chicken and set aside.
Reduce heat to low and melt butter in the pan. Add garlic and cook for 1-2 minutes until garlic is fragrant.
Sprinkle flour over the butter and stir, cooking 1-2 minutes until flour starts to brown. Next, slowly stir in milk and heavy cream, whisking to combine.
Add sundried tomatoes, spinach, seasonings, and chicken to the sauce.
Continue cooking about 4-5 minutes until spinach is wilted and sauce is thickened.
Stir in parmesan cheese and lemon juice.
Add pasta and toss with sauce until combined well.
