2 1/4 lb. Bartlett pears (about 5 total), peeled, cored and sliced 1/4 inch thick
1/4 c. cornstarch
1 tsp. ground cinnamon
1 tsp. finely grated lemon zest
1/4 tsp. salt
Make topping: In medium bowl, with hands, combine flour, oats, brown sugar, almonds, lemon zest and salt. Add butter and squeeze to form small clumps. Refrigerate until ready to use.
Heat oven to 375°F. Fit dough into bottom and up side of 9-inch pie plate. If necessary, trim dough so overhang is even all the way around (about 1/2 inch from edge of pie plate). Fold overhang under itself to create thicker rim of dough and crimp as desired. Refrigerate at least 20 minutes
Make filling: In large bowl, mash blackberries and granulated sugar. Add pears, corn-starch, cinnamon, lemon zest and salt and toss to combine.
Transfer to pie crust, top with crumb mixture and transfer to rimmed baking sheet. Bake until pears are tender and topping is golden brown, 1 to 1 1/2 hour, making sure to cover with foil if topping or crust begins to get too dark.