Roast or grill the onions, garlic, and ginger for a few minutes until charred.
In a large pot or pressure cooker, place the beef and bones and boil for 10 minutes. Strain out the impurities from the stock.
Add the grilled onions, garlic, and ginger. Bring to a boil then simmer. Remove any scum that appears.
Boil for about 3 hours or until meat is tender.
Add flavoring ingredients; bay leaf, fish sauce, soy sauce, sugar, and salt. Simmer over low heat for another 15 – 30 minutes to develop the flavor. Take out from the heat.
Place flat rice noodles in a bowl, spoon over broth, and top with beef slices, white onion slices, green onions, fried garlic, and drizzle calamansi juice to add flavor.