Hold the tail tube portion of the squid and with fingers, grasp the cuttlebone (the thin, clear cartilage inside the tube) and pull from the squid's body. Remove black ink and discard. Wash the squid and drain well.
Season squid with salt and pepper to taste. Let stand for about 10 to 15 minutes. Grill squid over hot coals for about 4 to 5 minutes on each side.
Remove squid from heat and allow to cool to touch. Chop into bite-size pieces and keep warm.
In a bowl, combine calamansi juice, Worcestershire sauce, brown sugar, and salt and pepper to taste. Stir until combined and set aside.
In a wide, heavy-bottomed skillet over high heat, add butter and oil.
Add onions, garlic, ginger, bell peppers, and chili peppers. Cook, stirring regularly, for about 30 to 40 seconds or until aromatic.
Add squid and calamansi mixture. Toss quickly just until heated through.
Season with salt and pepper to taste. Serve hot.
Make sure to set your heat on high, and your pan is sufficiently hot when the chopped squid are tossed with the onion mixture and the citrus dressing so they don't expel a lot of liquid.