Place the tomatoes, cucumbers, celery, red onions, yellow peppers, olive oil, lemon juice, and dill in a stainless-steel mixing bowl. Mix thoroughly. Season to taste with salt and pepper. Place in a non-reactive storage container. Cover and refrigerate until needed.
Place the peppers on paper towel to drain. Pat them dry. Chop finely. Place the peppers, mayonnaise, sour cream, mustard, and granulated onion and garlic in a stainless-steel mixing bowl. Whisk together thoroughly. Season to taste with salt and pepper. Transfer to a covered storage container and refrigerate until needed.
Place enough water in a large nonreactive pot to hold the 24 artichokes. Slice 6 lemons 6 mm thick. Place the lemons, garlic cloves, and bay leaves in the pot. Bring to a boil. Slice the last lemon in half. Cut off the bottom of the artichoke stem, leaving about 25 mm. Peel the stem using a vegetable peeler. Pull off any small, fibrous, dark leaves around the base of the stem. Using a serrated knife, slice off the top 12 mm of the artichokes. Trim off the sharp, pointed tips of the remaining leaves using a pair of scissors. Immediately rub the trimmed area of the artichokes with the halved lemon. This will prevent discoloration before cooking. Place the artichokes in the cooking liquid. Cover the pot. Reduce to a simmer 25–30 minutes. Cooking time will vary based on the size of the artichokes. The artichoke is done cooking when you can easily insert a knife into the stem or heart, or the leaves can easily be pulled off of the artichoke. Carefully remove the artichokes from the cooking liquid. Place them on a parchment-lined full sheet pan, stem-end up. Allow to drain. Remove any excess water from the tray. Refrigerate. Allow to cool. Slice artichokes in half lengthwise. Remove the small, spiny, tough leaves from the centre and discard. Using a melon baller or spoon, scrape the fuzzy choke portion from the bottom and discard. Place the alternating halves back together. Place in a covered storage container in a single layer. Refrigerate until needed.
To prepare à la carte:
Brush the inside halves of an artichoke with 15 ml of olive oil. Season to taste with salt and pepper. Place on a heated char-grill or broiler, oiled side down. Cook until just warmed through. Place on a warmed serving plate, grilled side up. Spoon 113 g of drained tomato cucumber relish over the top of the halves. Allow some of the relish to fill the cavity. Place the ramekin of roasted red bell pepper aioli at the top of the plate next to the artichoke.