Place pumpkin seeds in a blender; blend until mixture is powdery, 30 to 40 seconds. Set aside.
Cut beef into bite-sized cubes; season with salt.
Heat oil in a large pot over medium-high heat. Cook beef in hot oil until brown but not cooked through, 3 to 5 minutes.
Place tomatoes, onion, and peppers in a blender; blend until smooth, about 30 seconds. Stir tomato mixture into beef; reduce heat to medium-low and cover. Cook until meat is tender, 40 to 50 minutes.
Add shrimp, tomato sauce, water, and tomato paste; simmer for 10 minutes.
Stir in spinach and powdered pumpkin seeds. Continue simmering for 10 more minutes.