Make dressing: In a bowl, combine the harissa, water, salt, and lemon juice. Whisk in the olive oil and set aside.

Prepare the artichokes by removing the leaves and choke. Remove the stem, and pare off any hard green parts for the bottom of the artichoke. Put in acidulated water to prevent discoloration. Using a madoline or very sharp knife, thinly slice the artichoke bottoms and toss with the dressing. Let marinate for 15 minutes.

Divide the artichokes among four plates, and sprinkle with the capers, mint, and garnish with finely diced tomato.