Method:

1. Cook the pasta al dente in salted water, strain and set aside, reserving 1,5 cups of the pasta water 
2. In a large pan over medium heat, melt 3/4 of butter and add the bacon and onion and cook until translucent.
3. Add in the garlic and chilli flakes and cook for 1 minute.
4. Add imifino and cook for 5 minutes, stirring occasionally. Add 1 cup of the pasta water and using an immersion blender, pulse into a chunky sauce. 
5. Stir in the zest, cheese and lemon juice and season with salt and pepper. 
6. Add the pasta and the remaining butter. If the sauce is too thick, loosen with the remaining pasta water