Peel the beets and then cut them up into small squares. Cook covered at 375 for 1.5-2 hours or until cooked (not mushy, just cooked).
In a large pan, heat up the olive oil for about 2 minutes on medium, then add fennel seeds.
After about 4 minutes, add the orange juice.
Once the dressing has simmered for about 5 minutes, add the cooked beets and ensure they are all covered with the dressing. Add salt and pepper to taste.
Let the beets cool a bit - not too much.
Lay out the spinach and place warm beets and dressing over it. Serve it right away - you don't want the spinach to wilt and get soft.
Eat up and enjoy this salad treat.