How to Make It
Prepare the crust: Pulse pine nuts in a food processor until finely chopped. Add flour, powdered sugar, dry milk, and 1/2 teaspoon salt; pulse to combine. Add butter; pulse until mixture resembles sand. Combine oil and ice-cold water in a small bowl. With processor running, slowly pour oil mixture through food chute; process until dough is moistened and beginning to clump. Divide dough evenly between 2 (14- x 4 1/2-inch) removable-bottom metal tart pans lightly coated with baking spray; press evenly into bottom and up sides of pans. Prick dough all over with a fork; freeze 1 hour.
Preheat oven to 400°F.
Remove dough from freezer; bake at 400°F until lightly golden, 10 to 12 minutes. Transfer to a wire rack to cool. Reduce oven temperature to 350°F.
Prepare the filling: Combine granulated sugar, lemon zest, and lavender in a large saucepan; rub zest and lavender into sugar with your fingers to release oils. (Sugar will be slightly moist and will release lemon and lavender scents.) Stir in 2% milk, half-and-half, rice, and 1/2 teaspoon salt. Cook over medium, stirring often, until mixture thickens and rice is tender, 35 to 40 minutes. (Do not allow mixture to come to a boil.)
Lightly beat egg yolks in a medium bowl. Whisk a few tablespoons of liquid from the rice mixture into egg yolks. Add egg yolk mixture to rice mixture, stirring constantly. Cook, stirring constantly, until slightly thickened, 2 to 3 minutes.
Spoon filling evenly into crusts (about 2 cups per crust), smoothing with a rubber spatula. Stir together jam and lemon juice in a small microwave-safe bowl; microwave at HIGH until hot, about 20 seconds. Dollop onto tarts; swirl lightly with a knife. Bake at 350°F just until set, about 8 minutes, rotating pans halfway (on same rack) after 4 minutes. Cool completely on wire racks; refrigerate 8 hours or overnight. Remove tarts from refrigerator; remove sides of pans. Cut each tart into 6 slices.