Make sure rice is fully cooled. It's best to use leftover rice for this!
Heat oil in a deep non-stick frying pan. Sauté the onions and spam until onions are soft and lightly golden.
Add another tablespoon of oil if needed before adding rice. Add cooked, cooled rice, breaking up the clumps, frying until heated through, about 5-7 minutes.
Pour egg over rice, occasionally turning over and stirring until egg is completely cooked.
Drizzle soy sauce in a spiral motion over the rice, stir to combine well. Remove from heat and cover with a lid to “steam” a little, about 5 minutes.