Combine pasta, sliced chicken sausage, lemon zest, sliced garlic, olive oil, salt, and 4 1/2 cups water in a large pot over high heat. Once the water is boiling, reduce heat to medium-high and set a timer for 10 minutes. Stir occasionally to keep the pasta from sticking to the bottom of the pot.
After 10 minutes, add the kale and lemon juice and cook for an additional 2-3 minutes, until the pasta is al dente and about 90% of the water is gone and a thick sauce has formed, then remove the pasta from heat.
Add fresh cracked black pepper, parmesan cheese, and red pepper flakes, capers and toss to combine. Serve immediately.