Mince onion and garlic, finely chop the tomato.
Cook finely diced onion in a tablespoon of the oil over medium heat until tender. Stir frequently for 6 minutes, allowing the onion to slowly sweat (set aside 1 cup of hot water to add as needed to prevent browning).
Add the rest of the oil and cook until onions are translucent and tender, for about 2 minutes.
Add in the tomato and mix, allowing for the sauce to cook down, approximately 6 minutes.
Add garlic and sauté, adding splashes of water as needed. Cook until fragrant, about 1 minute.
Add what is left of the 4 cups of water, and bring to a boil.
Pour in the shiro powder and stir frequently to ensure the mixture is not lumpy. Keep high heat for another 4 minutes.
Reduce heat slightly so that the mixture is simmering, not boiling. The shiro will thicken as it simmers; add water as needed to arrive at desirable texture and thickness.
Stir in the bessobela, add sea salt to taste, and garnish with Jalapeno (optional).
