Blanch the spinach in boiling water for 2-3 minutes until wilted.
Drain and immediately transfer the spinach to ice water to retain its color.
Blend the spinach into a smooth paste and set aside.
Heat oil in a pan and add cumin seeds; sauté until they crackle.
Add chopped onions and sauté until golden brown.
Stir in minced ginger and garlic; cook for 1-2 minutes.
Add the pureed tomatoes and cook until the oil separates.
Mix in the spinach paste and add salt; cook for 5 minutes.
Add paneer cubes and gently mix; simmer for another 5 minutes.
Sprinkle garam masala on top and serve hot.