Humble lentils get lavish treatment with vinegar-soaked cherries, roasted peppers, and a tangy dressing that uses the cherry-infused vinegar. It works as a wholesome, gorgeous side or a vegetarian main—and it tastes even better after marinating in the fridge for a few days!
Rinse and pick through the lentils to remove stones and other detritus. Add to a large pot and cover with water; add salt and bay leaf. Bring to a simmer over medium-high heat; then cook uncovered until lentils are tender but still firm, not mushy, about 20 minutes. Meanwhile, toss the cherries with the vinegar in a small mixing bowl. Set aside to soak.
Drain cooked lentils and transfer to a large bowl; discard the bay leaf. Peel shallot and cut it in half lengthwise. Lay the halves flat on a cutting board; finely slice the halves lengthwise, stopping at the root so the shallot stays intact. Then slice crosswise to mince. Add minced shallot to the lentils, along with ¾ of the macerated cherries, reserving the vinegar. (Add remaining cherries to taste.)
Slice open the piquillo peppers so they lie flat. Scrape and discard the seeds. Stack peppers and chop into a small dice. Add to the lentils, along with the mustard, a pinch of salt, and 3 tablespoons olive oil. Toss to combine, then adjust to taste with more cherry vinegar, the remaining oil, and salt as needed. Optional: Let rest 30 minutes before serving so the flavors can meld.
Just before serving, finely chop the chives into ¼-inch pieces. Toss into the lentils and serve warm or at room temperature.
Store Lentil Salad in an airtight container, refrigerated, for up to a week.