Step 1
Combine zest of 1 lemon, 1 cup whole-milk ricotta, 2 tsp. honey, and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt in a food processor; season with freshly ground pepper. Process until ricotta is fluffy and mixture is smooth, about 2 minutes. Set aside.
Step 2
Heat 1 Tbsp. extra-virgin olive oil in a large cast-iron skillet over medium. Cook 2 thick-cut slices sourdough bread, cut in half crosswise, until golden brown and crisp underneath, about 4 minutes. Transfer bread to plates and turn fried side up. Repeat with another 1 Tbsp. extra-virgin olive oil and remaining 2 thick-cut slices sourdough bread, cut in half crosswise. Wipe out skillet.
Step 3
Heat remaining 2 Tbsp. extra-virgin olive oil in same skillet. Cook one 12-oz. jar marinated artichoke hearts, preferably grilled, drained, and one 2-oz. jar capers, drained, stirring occasionally, until artichokes are dark brown in spots, capers are darkened in color, and skillet looks dry, 5–8 minutes.
Step 4
Meanwhile, combine 3 red radishes or 1 small watermelon radish, trimmed, thinly sliced, and 2 cups coarsely chopped mixed tender herbs (such as basil, chives, dill, and/or mint) in a small bowl. Add 1 Tbsp. fresh lemon juice and reserved 1 Tbsp. artichoke marinade and 2 tsp. caper brine; toss to coat.
Step 5
Mound reserved whipped ricotta on toasts. Top with artichoke mixture, then herb salad. Season with pepper.
Do ahead: Whipped ricotta can be made 2 days ahead. Cover and chill.