I once thought that the acidity of citrus and the spiciness of radishes would clash, but it turns out they rather complement each other. In this recipe it could be that the radishes marinate for a bit in the citrus juice, and this tames the spiciness. As well the addition of oil cuts the acidity of citrus. You can use lemon, lime, or orange juice. here, though I think that orange juice is better with winter radishes, such as daikon. Japanese turnips are good here too. This makes a nice and quick side dish. The ingredient amounts are purposely vague here, it all depends on the quantity of radishes you have on hand.
lemon, lime, or orange juice
extra-virgin olive oil, or other salad-type oil
sea salt, to taste
finely chopped scallion greens, for garnish
1. Thinly slice or dice radishes. Put in a bowl. Add lemon juice, perhaps starting with a tablespoon. Ditto with the olive oil. Sprinkle with some, not too much, salt. Gently toss. Taste a piece and add more of any of the dressing ingredients. Generally one uses more oil than acid in a dressing.
2. Allow to marinate at room temperature for 20 minutes if you can. The salt will draw some moisture from the radishes. Gently stir before serving.