Potato and Onion Casserole [oil-free, gluten-free, vegan]

8-10 medium-sized yellow (Yukon Gold) potatoes, sliced into 1/8-inch slices (do not peel!)
1/2 yellow onion, sliced thinly
1/4 t each of paprika, garlic powder, onion powder, and salt
1/8 t black pepper to taste
1/4 cup vegetable broth
ketchup (optional)

Preheat oven to 400 degrees.
Mix spices together in a small bowl.
Layer 1/3 of the onions on the bottom of an 8x8 casserole dish
Layer 1/3 of the sliced potatoes on top of the onions.
Sprinkle with 1/3 of the spice mixture.
Make two more layers following the steps above.
Pour the vegetable broth over the top of the potatoes gently, so as not to wash off the seasoning.
Bake (uncovered) for about 40-55 minutes until the potatoes are tender (test with a fork) and the top is lightly browned. Serve warm with ketchup, if desired.