In a mixing bowl, combine tomatoes, scallions, red onions, 1 teaspoon cumin, 1/3 cup olive oil, sherry vinegar, and serrano. Season with salt and pepper, to taste. Set aside for 2 hours.
In a large stock pot place white beans and cover with 3 times the amount of water. Add bay leaf. Boil until beans are tender at least 1 hour. Strain beans.
In a medium size saute pan, saute onions and garlic with 1/3 cup olive oil until translucent. Add oregano and 1 tablespoon cumin until aromatic.
In a food processor, puree beans and onion mixture. Season with salt and pepper. Set aside.
Season the mahi mahi with salt and pepper. In a medium size saute pan, heat a little olive oil and cook the mahi mahi for 3 to 4 minutes on each side.
To serve, place puree in large serving platter. Set fish on top of puree and top with tomato relish.