Bring a large pot of well-salted water to a boil. Cook the pasta until just al dente, about 1 minute less than package directions. Reserve 1 cup of pasta water before draining.

Place the chicken breast between two sheets of plastic wrap and gently pound to an even thickness of about 1/2 inch (1.25 cm) using a rolling pin.

Season the chicken generously on both sides with salt and pepper, then dust with the flour, shaking off any excess.

Heat the olive oil in a large skillet over medium-high heat. Cook the chicken for 2 minutes per side, or until golden and cooked through (internal temperature of 165°F). Transfer to a plate and tent loosely with foil.

Reduce heat to medium. Add the butter to the skillet. Once melted, add the garlic and cook gently for about 1 minute, stirring, until fragrant but not browned.

Stir in the rosemary and cook for another 30 seconds.

Pour in the heavy cream and bring to a gentle simmer, adjusting heat to keep it from boiling.

Gradually add the Parmesan cheese in 2 to 3 additions, stirring well after each until melted and smooth.

Season with black pepper and lemon juice, stirring to combine.

Add 1/4 cup of the reserved pasta water and let the sauce simmer gently for 2 to 3 minutes, until it thickens slightly.

Add the drained pasta to the skillet and toss well to coat. Let it bubble gently for 1 to 2 minutes, adding a splash more pasta water if needed to maintain a creamy consistency.

Slice the chicken breast into strips. Serve the pasta topped with the chicken, or toss the chicken slices through the pasta.

Garnish with additional rosemary leaves, lemon zest, and extra Parmesan if desired.