Heat olive oil over medium-high heat in a large skillet. Add garlic slices then cook, stirring near constantly, until slices are pale golden brown. Remove to a plate and set aside.
Turn heat down to medium then add red onion. Season with salt and pepper then cook until golden-brown and tender, about 3 minutes. Add cranberries and kale, season with more salt and pepper, then add water, place a lid on top of the skillet and cook for 4-5 minutes, or until kale is tender.
Add spaghetti to a large pot of salted, boiling water then cook until al dente.
Add Kalamata olives to cooked kale and cranberry mixture. Transfer cooked spaghetti to skillet then toss to combine all ingredients. Add up to 1/4 cup pasta cooking water if needed. Divide between two plates then top with 1 Tablespoon feta cheese and half the cooked garlic slices each.
Jessianna Saville, MS, RDN, CSR, LD, CLT discovered the original recipe at Iowa Girl Eats.