Preheat oven to 400 degrees and place oven rack in center position. Place a medium sized pot of salted water to boil. While you wait for water prepare bread crumbs.

Place 1 slice of sourdough bread (torn), 3/4 cup parmesan, and olive oil into a food processor and mix until well combined. Place onto a baking sheet and bake for 6-7 minutes. While bread crumbs bake chop parsley and zest lemon. Set aside.

When water is boiling, cook pasta to package instructions.

Remove bread crumbs from oven, toss with parsley, lemon zest and red pepper flakes, set aside. Make brown butter:

Place a small pan on cooktop on medium heat. Add butter, bring to a simmer (you may need to lower the temp a little once it gets going) When butter is slowly simmering, stir here and there. After 3-4 minutes the butter will start to brown. Once it's brown turn off heat.

Place spinach in a large bowl. When pasta is ready, remove 1/4 cup pasta water, set aside. Strain pasta, do not rinse! Immediately add pasta to bowl on top of spinach. Allow to sit for 60 seconds, so spinach can wilt. Pour browned butter over pasta and toss, add pasta water and toss again. Sprinkle with generously sea salt and pepper. (If needed you can drizzle a little olive oil over pasta)Top with half of the bread crumbs, toss again. Sprinkle with remaining bread crumbs and remaining parmesan cheese. Serve and enjoy!