To prepare Bagoong at Mataba na Alimango dish, you will need the following ingredients:

- 4 large fat crabs (alimango)
- 1 cup bagoong (fermented shrimp paste)
- 1 medium onion, minced
- 3 cloves garlic, minced
- 2 tomatoes, chopped
- 2 cups water
- 2 tbsp cooking oil
- Salt and pepper to taste
- Chili peppers, optional for added heat
- Green onions, chopped for garnish

Here's how to prepare it:

1. In a large pan, heat the cooking oil over medium heat. Add the onions and garlic and sauté until fragrant.

2. Add the tomatoes and cook until they are soft and mushy.

3. Add the bagoong and water to the pan and stir to combine. Let it simmer for a few minutes to allow the flavors to blend.

4. Clean the crabs by removing the gills and the apron. Cut them into halves or quarters, depending on your preference.

5. Add the crabs to the pan with the bagoong mixture. Cover and let it cook for about 15-20 minutes or until the crabs turn orange and are fully cooked.

6. Adjust the seasoning with salt and pepper. Add chili peppers if desired for added heat.

7. Transfer the cooked crabs to a serving platter and garnish with chopped green onions.

8. Serve hot with steamed rice. Enjoy your delicious Bagoong at Mataba na Alimango dish!