Begin by filling a large pot with water and bringing it to a rolling boil. Add salt and toss in your pasta. Cook according to package instructions until al dente, around 8-10 minutes, reserving ½ cup of pasta water before draining.

Season thinly sliced chicken breasts with garlic powder, salt, and pepper. Heat olive oil and butter in a skillet over medium-high heat. Cook chicken for 5-6 minutes on each side until golden and cooked through. Remove and let rest before slicing.

In the same skillet, reduce heat and add all-purpose flour. Stir into drippings and cook for 1 minute. Gradually pour in chicken broth, scraping the skillet for flavor. Cook until it begins to thicken, about 2-3 minutes.

Lower the heat; stir in heavy cream, pesto, and lemon juice. Mix until fully combined and let simmer for 4-5 minutes until slightly thickened.

Add fresh baby spinach to the sauce, stirring until it wilts down in 2-3 minutes.

Add drained pasta to the skillet, tossing to coat. Adjust consistency with reserved pasta water if necessary. Top with sliced chicken and Parmesan cheese before serving.