Fill a large pot with lightly salted water and bring to a rolling boil. Stir in pasta and return to a boil. Cook pasta uncovered, stirring occasionally, until tender yet firm to the bite, 8 to 10 minutes. Reserve 1/2 cup pasta water. Drain pasta and set aside.

Melt 1 tablespoon butter in a skillet over medium heat. Add garlic; fry until fragrant, about 1 minute. Add remaining butter and melt, then sprinkle in flour. Whisk to combine; cook for about 1 minute.

Whisk chicken soup base into reserved pasta water; pour into skillet. Whisk to make a smooth sauce. Whisk in lemon juice, 1 tablespoon at a time, to taste. Stir in parsley and capers. Season with salt and pepper. Allow to simmer until sauce thickens, about 2 minutes.