Place flour in a small bowl or plate. Sprinkle chicken breasts evenly on both sides with garlic powder and a small amount of salt and pepper.

Warm olive oil and 1 Tablespoon of the butter in a large skillet over medium-high heat. Lightly dredge each chicken breast through the flour on both sides. Shake gently to remove any excess, then place each piece in the hot pan. Cook for 1-2 minutes per side, until browned on the outside but not quite fully cooked through. Remove chicken pieces and set aside.

Add remaining 2 Tablespoons butter to the pan, plus garlic. Cook for about 30 seconds, just until fragrant, then add the broth, wine, Italian seasoning, and tomatoes. Bring the liquid to a simmer and let it bubble for 1-2 minutes, scraping the bottom of the pan to remove any browned bits.

Return chicken to the pan, lower heat to medium-low, and simmer for another 3-4 minutes, until the sauce thickens slightly, the tomatoes start to lose their shape, and the chicken is cooked through.

Remove pan from the heat, then tuck the baby spinach around and under the pieces of chicken. Let it wilt for about 1 minute.

Squeeze lemon juice over each piece of chicken, and season with extra salt and pepper to taste. Serve right away.