Wash the spinach until the water runs clean, drain. Shred the spinach to make about 3 cups.
Heat 3 tablespoons of the olive oil in a deep skillet. Add the scallions, onions, a pinch of salt, and 1/2 water and cook, covered, over medium-low heat for 10 minutes.
When the water evaporates, slowly let the onions turn golden, stirring occasionally. Add 2 cups water, the tomato paste, and rice. Cover and cook 10 minutes.
Spread the spinach and dill over the rice, cover, and cook 10 minutes longer.
Remove from heat, mix, then place a double thickness of paper towels over the rice. Cover again and let stand until cool. Adjust the seasoning with black pepper and salt.
Drizzle with the remaining olive oil. Serve at room temperature garnished with olives and feta.