In medium bowl, toss 2 cups raspberries with granulated sugar, ¼ teaspoon vanilla and lemon juice until evenly coated. Let sit 10-15 minutes, until berries release juices.
Meanwhile, in large bowl, whisk cream, powdered sugar, pinch of salt and remaining ¼ teaspoon vanilla until soft peaks form.
Use potato masher to mash raspberries into smooth puree. Fold about ¾ puree into whipped cream until just combined.
Lightly crush about 12 shortbread cookies (you'll want some large pieces for texture) and fold into whipped cream.
In glass trifle bowl, layer almost ½ remaining raspberry puree, ⅓ whipped cream and more crumbled cookies. Repeat layers of puree, whipped cream and cookies. Finish with swirl of raspberry puree, a few fresh raspberries and 1 whole cookie. Serve, refrigerating any leftovers.
