Rinse the grapefruit/pomelo. Peel off the outer yellow skin, remove the flesh of the fruit from the pith. (You can use the outer yellow skin to make yuzu salt.)
Cut the pith into 1-inch cubes.
Add the pith cubes to a large pot, fill the pot with enough cold water to cover the pith cubes. Bring the water to a boil over high heat.
Turn off the heat, transfer the pith cubes into a large bowl.
Wash the pith for at least 3 times to get rid of the bitter taste. Pretend you're washing small sponge cubes: Soak the pith in cold water, squeeze out all excess water, change the water for 3 - 4 times until the water turns from green to clear.
Add sugar and water to a large frying pan, bring to a boil over high heat, add pith cubes to the pan.
Stir the pith cubes with a spatula over high heat for about 10 minutes until there is no water at the bottom of the frying pan. Use the spatula to gently press the pith cubes to squeeze out the excess water.
Reduce heat to medium high, keep frying for about 20 more minutes until sugar crystals start to present on the frying pan.
Reduce heat to medium, keep frying for 5 to 10 minutes until the pith cubes form a crystallized outer layer. When you shake the pan, you should be able to hear the rustling sound. The candied grapefruit peel or pomelo peel should feel dry to touch.
Transfer out to a plate, let cool to room temperature before serving.
Video
Notes
1. You can use the yellow pomelo/grapefruit skin to make yuzu salt.2. To wash off the crystalized layer on the spatula and the frying pan: add plenty of water to the frying pan until all the sugar crystals are covered, bring the water to a boil over medium high heat, reduce heat to low, let simmer until all the sugar crystals are melted.3. To store: stored in the refrigerator in an airtight container for up to 1 month. If the surface starts to feel damp or sticky, pour the candied grapefruit peel to a frying pan, fry over medium heat for 5 to 10 minutes until the dry crystalized outer layer forms again.