Wash the fruit and dry well. Using a vegetable peeler, cut lengths of peel from the fruit, avoiding as much of the bitter white pith as possible. Scrape off any pith still on the peel with a small spoon. Cut each piece of peel into 2-3mm strips.
Put 200g sugar in a medium saucepan and add 200ml water. Bring to the boil and simmer for about 5 minutes, until lightly thickened. Add the strips of peel, reduce the heat to low and simmer for 10-15 minutes, until the peel turns translucent.
Using a slotted spoon, transfer the peel pieces to a sieve and drain well. Put the remaining 3 heaped tbsp sugar and the citric acid into a plastic ziplock bag and shake to combine. Add the drained peel and shake to evenly combine.
Transfer the coated peel to a piece of baking paper, arrange in an even layer and leave to dry (a few hours).for the salad
Juice one of the pink grapefruit and add the juice to a medium bowl. Slice the fennel as thinly as possible (a mandoline is great for this) and add to the juice. Marinate the fennel in the grapefruit juice for a few hours, up to overnight.
Segment the remaining pink grapefruit and blood orange, discarding all the pith (see this tutorial on How to segment citrus if needed).
Either arrange all the salad components on a large platter for people to share or assemble the salads individually with a small heap of marinated fennel, 2 grapefruit segments and 2 blood orange segments on each plate.
Drizzle everything with the pomegranate molasses, sprinkle with a little flaky sea salt and top with the candied citrus peel. Gold dust optional!