Use the shredding blade of the food processor to shave the Brussels sprouts into thin pieces; you may have to work in batches. Or slice them thinly crosswise by hand.
Transfer the sprouts to a large bowl and add a large pinch salt. Gather handfuls of the shreds together, rubbing, lifting, and separating them until the salt is distributed and the shreds soften a bit.
Add the olive oil, lemon juice, onion, and a generous sprinkle of pepper. Toss thoroughly and refrigerate for at least 1 hour or up to 6. Taste and adjust the seasoning, adding more lemon if you like, and serve cold or at room temperature.
5 Flavorful Additions to Brussels Sprouts Salad
Alone or in combination, just toss them in. In some cases, you’ll want to wait to add salt until after tasting.
1/2 cup grated Parmesan or manchego cheese
1/2 cup chopped pitted black or green olives
1/2 cup dried fruit, like raisins or cranberries, or chopped dried apricots, plums, or dates
1/2 cup chopped nuts, like hazelnuts, almonds, walnuts, or pecans