Stem and slice ⅔ of the strawberries (for about 4 cups); reserve the rest for serving. Toss the sliced strawberries with 3 tablespoons of the sugar, the lemon juice, and the Aperol in a nonreactive bowl; set aside to macerate for about 15 minutes to allow the fruit to give off some juices.
Add ⅔ of the strawberry mixture to a blender along with the jam. Puree until almost smooth, then stir this puree back into the bowl of macerating strawberries. Using an electric mixer on medium speed, beat the mascarpone and yogurt in a large bowl just until smooth and combined, about 1 minute. Do not overbeat.
In another bowl, beat the cream with the remaining remaining ⅓ cup sugar, vanilla, and lemon zest until soft peaks form. (Tip: The slower you beat the cream at the beginning, the better it will hold its air bubbles.) Fold ¼ of the whipped cream into the mascarpone mixture to lighten, then fold in the rest of the whipped cream in 2 batches.
To assemble, spread ½ of the strawberry sauce into the bottom of an 8-by-10-inch or a 9-inch casserole dish. Dip a ladyfinger in the sauce in the dish, turning to coat both sides. Repeat with 13 more ladyfingers, nudging them closely (cutting them as needed to fit, per headnote). Spread with half the mascarpone cream, then the remaining strawberry sauce. Add the rest of the ladyfingers and top with the remaining mascarpone cream, spreading evenly.
Cover with plastic wrap (or lay a piece of parchment on top if the dish is overfull) and refrigerate for at least 6 hours, preferably overnight. (It will keep for up to 2 days at this point.)
When ready to serve, stem and slice the reserved strawberries. Arrange them over the tiramisu, overlapping the slices, then scatter with the pistachios and a handful of raspberries if desired. Cut into squares—or scoop out with a large metal spoon.