Preheat oven to 350 degrees F.
Layer the lemon slices in the bottom of a casserole dish (needs to be big enough to fit salmon in one layer).
Mix yogurt, garlic, spinach, olive oil, dried dill, salt, pepper, and capers in a bowl.
Place salmon on top of lemon slices.
Cover salmon with yogurt mixture.
Cover casserole dish tightly with aluminum foil or other tight cover.
Bake covered for 20 minutes, uncover and continue baking for 10-20 minutes more, or until salmon is flaky and no longer pink in the middle. Drain excess liquid if necessary.
