In a large, deep skillet over medium heat, warm ¾ cup of olive oil until hot and shiny. Gently tip in the onions and stir to coat them in the oil. Increase the heat to medium-high and cook, stirring frequently, for about 20 minutes, or until the onions are tender, floppy, and yielding—they should be deeply golden brown but not completely caramelized. Remove from the heat and set aside.

Meanwhile, in a large pot with a tight-fitting lid, combine the broth or water, lentils, and cumin. Add the salt, but use less if your broth is salty. Bring to a boil, then lower the heat and simmer, adding more water if needed, until the lentils are tender but not mushy, 15 to 30 minutes depending on your lentils. Drain the lentils and return them to the pot, reserving the cumin-scented lentil water. Measure this water. If you don’t have 4 cups, add broth or water to make up the difference.

Add the bulgur, along with the 4 cups of lentil water, to the lentils in the pot and bring to a boil. Continue boiling for 3 minutes, then remove from the heat, cover, and let stand until the bulgur is completely hydrated and tender and the lentils are soft, 15 to 20 minutes. The liquid should be completely absorbed at this point; if it isn’t, turn the heat back on low and stir gently until it is. Taste and season with salt.

In a very large salad bowl, toss the lentils and bulgur with the cooked onions, lemon juice, the big glug of finishing olive oil, the dates, and the arugula. Get everything evenly distributed, then taste and finesse with flaky salt, pepper, and more olive oil if needed. Serve hot or at room temperature. Leftovers will keep, in an airtight container in the refrigerator, for a couple of days, and up to a week if you leave the arugula out and only add before you want to eat.