Place black-eyed peas in 8 quart pot. Add enough water to fill pot 3/4 full. Stir in ham and diced onions, and season with salt, pepper, and garlic powder. Place tomatoes in a blender or food processor, and blend until the tomatoes are liquefied. Add tomatoes to pot. Bring all ingredients to boil. Cover the pot, and simmer on low heat for 2 1/2 to 3 hours, or until the peas are tender.