Bring a large pot of water to a full boil and salt it lightly.
Blend cottage cheese, 1/2 cup Parmesan, lemon zest, lemon juice and black pepper for 45 to 60 seconds until glossy and smooth.
Cook garlic and optional red pepper in olive oil over medium-low for 60 to 90 seconds until fragrant and pale gold; turn off heat.
Boil pasta according to its package, beginning checks 2 minutes early; reserve at least 1 cup hot pasta water before draining.
With the blender on low, stream 1/2 cup hot pasta water into the cottage cheese mixture and blend 10 seconds.
Add drained pasta and spinach to the skillet, pour over sauce and toss with the burner off, adding pasta water gradually until glossy.
Fold in remaining Parmesan, taste before adding salt and serve immediately with herbs and black pepper.
