How to Make It
Preheat oven to 375°F with rack in lower third of oven. Line bottom of oven with aluminum foil or an oven liner. Lightly coat a 12-cup muffin pan with non-stick spray.
Stir together ¾ cup of the brown sugar and ¾ cup plus 2 tablespoons of the flour in a medium bowl. Stir in cinnamon. Cut butter into flour mixture with a pastry blender until large, moist clumps form. Fold in almonds. Cover and chill until ready to use.
Working with 1 piecrust at a time, cut 2 6-inch circles from each piecrust. Fit a 6-inch piecrust round into each cup of prepared muffin tin, pressing and flattening into muffin cups and leaving about ½-inch overhang. Fold overhang under, and crimp or flute edges. Chill until ready to use.
Combine plums, cranberries, orange zest, salt, remaining 1¼ cups brown sugar, and remaining 2 tablespoons flour in a large bowl and toss to combine. Spoon about ½ cup fruit mixture into each prepared piecrust, filling about three quarters of the way full. Top each pie with 2 tablespoons of the almond crumble.
Bake on lower rack until crust is golden and filling is bubbly, 40 to 45 minutes, tenting with foil after 30 minutes if browning too quickly. Remove from oven, and cool in pan 5 minutes. Gently remove pies from muffin tin and transfer to a wire rack. Let cool completely, about 45 minutes.