Combine minced garlic, liquid seasoning, soy sauce, peppercorns, paprika, calamansi juice in a bowl and mix until the ingredients are dissolved.
Add in the tuna, stir until the tuna are coated with the marinade. Marinate for at least 15 minutes.
In a medium size skillet, heat oil and saute the chopped garlic until fragrant. Remove the garlic from the pan and set aside.
In the same pan or skillet with the heated oil, fry the tuna cubes and stir for no more than 5 minutes until the all the sides are completely seared. Then remove from pan, drain and set aside. Remove excess oil from the pan and leave about 1 tablespoon of oil.
In the same pan, put butter, oyster sauce and about half a cup of water. Bring to a boil until the butter is dissolved for about a minute.
Add in the fried tuna cubes and garlic and stir until it is well coated with the sauce for about 3 minutes. Adjust seasoning with salt and pepper if necessary. Serve hot.