Drain and rinse the hearts of palm under cold running water, then slice each piece in half lengthwise and cut it crosswise into bite-size pieces. Rinsing off the packing brine is what keeps the ceviche tasting bright instead of salty and pickled.

Put the hearts of palm in a large bowl, pour over the lime juice and orange juice, and set it aside to marinate for 20 to 30 minutes. The citrus is what gives the mild palm its flavor, so give it that time before anything else goes in.

While the palm marinates, soak the sliced red onion in a bowl of ice water for 10 minutes, then drain it well. Ice water pulls the harsh bite out of the onion so it stays crisp without dominating the bowl.

Make the dressing: pour 1/4 cup of the citrus from the palm bowl into a small blender, add the garlic, half of the cilantro, and a few pieces of the jalapeno and palm, and blend until smooth. Whisk in the olive oil, cumin, salt, and black pepper. This quick plant version of leche de tigre is what makes the dressing cling and season every bite.

Add the drained onion, tomatoes, and remaining jalapeno to the marinated hearts of palm, pour over the blended dressing, and toss to combine. Taste and add more salt or lime juice if the bowl needs a lift.

Just before serving, gently fold in the avocado and the rest of the cilantro so they hold their shape. Spoon the ceviche into bowls or onto tostadas and finish with a little extra cilantro. Serve cold with tortilla chips or tostadas for scooping.