I like to use a hot, whole-grain mustard here because the spiciness adds another dimension of flavor to the salad. The vinegar in this recipe builds on the tartness of the citrus fruits but also brings in a little sweetness.
For the lemon-Dijon vinaigrette:
Combine the lemon zest and juice, vinegar, mustard, garlic and oil in a glass jar with a large pinch of salt and a few grindings of pepper.
Seal the jar tightly and shake well. Season to taste with salt and pepper. Shake again just before serving.
For the salad:1.
Cut the lemon in half, squeeze the halves into a medium bowl and drop in the rinds. Add cold water to a depth of 4 inches or so.2.
Pull the rough outer leaves off the artichoke. You do this first step by hand because you have more control that way. Turn the artichoke upside down and cut off all the dark green leaves with a sharp paring knife, turning the artichoke in your hand while you slice with the other. Turn it right side up, trim the stem to 1 inch, and run the knife up the stalk to remove all the darker green peel around the stem. As you cut, keep dipping the artichoke and knife in the acidulated water to prevent oxidation. Cut off and discard the purple flower at the top, then scoop and scrape out the furry choke in the center. Keep the remaining heart in the acidulated water.3.
Pick off and reserve the fronds from the top of the fennel. Run the fennel bulb and stems on a mandoline to create paper-thin slices, then mandoline the artichoke heart as well. Toss the fennel and artichoke slices in a large bowl with the dressing to prevent oxidation.4.
Trim the top and bottom of the grapefruit, then use a paring knife to cut off all the pith and peel. Reserve the peels. Holding the grapefruit over the fennel and artichokes, cut out the segments between the membranes, letting them drop into the bowl. Squeeze all the juice you can from the membranes, then discard. Gently toss and add more dressing to taste.5.
Divide the mixture among serving plates and top with the parsley, avocado and ricotta salata. Zest some of the reserved grapefruit peel on top, then sprinkle with the reserved fennel fronds. Season with salt and pepper and serve immediately.