Greek Spanakorizo Σπανακόρυζο

Name: Greek Spanakorizo (Σπανακόρυζο)
Ingredients: ¾ cup long grain rice; 24 ounce chopped frozen spinach; ½ small red onion finely chopped; 4 green onions (or spring onions), chopped; 1 clove garlic, minced; ¼ cup parsley, chopped; ½ cup Greek extra virgin olive oil; 2 - 8 ounce cans tomato sauce; 1 tablespoon tomato paste; 2 cup water; Salt & pepper to taste; 2 lemons; 1 juiced; 1 sliced for serving / garnish; ¼ cup imported Greek feta, crumbled