Bring a large pot of generously salted water to a boil. Cook pasta according to package directions until just al dente. Before draining, scoop out 1/2 cup of pasta water and set aside. Drain and set pasta aside.

While pasta cooks, heat olive oil in a large skillet over medium-high heat until shimmering. Add chicken pieces in a single layer, season with salt, pepper, and garlic powder, and cook for 6 to 8 minutes until golden and cooked through to 165°F. Work in batches if needed to avoid crowding. Remove and set aside.

Reduce heat to medium. Melt butter in the same skillet, scraping up any browned bits from the chicken. Add minced garlic and sun-dried tomatoes and sauté for 1 minute until fragrant.

Pour in the heavy cream and bring to a gentle simmer over medium-low heat. Add the Parmesan in a slow stream, whisking until melted and the sauce begins to coat a spoon, about 2 to 3 minutes.

Stir in the fresh baby spinach and cook for no more than 60 seconds until just barely wilted and still bright green.

Add the drained pasta and seared chicken to the skillet. Toss everything together to coat in the sauce. If the sauce is too thick, add reserved pasta water one tablespoon at a time until it reaches your preferred consistency.

Plate immediately and garnish with fresh basil or parsley and red pepper flakes. Serve hot.