Heat the olive oil in a skillet over medium heat. Add the garlic and onion and cook for about 2 minutes until softened.
Add the baby spinach and cook until it is wilted, about 3 minutes. Then, remove the skillet from the heat and let the mixture sit for 5 minutes.
While the spinach rests, bring a large pot of salted water to a boil and cook the pasta until al dente. Reserve 1/2 cup of the pasta water and drain the pasta.
In a blender, combine the spinach mixture, ricotta, lemon juice, Parmesan, onion powder, and 2 tablespoons of the reserved pasta water. Blend until smooth, and season with salt and pepper. Add more reserved pasta water if needed to reach your desired consistency.
Toss the cooked pasta with the blended sauce in a pan over low heat for 1-2 minutes. If desired, garnish with fresh basil and additional Parmesan cheese when serving.