After peeling and coring the pears, slice them lengthwise about 1/8" thick. Don't slice them too thick or the pie won't cook to be soft enough, not too thin or the pears will disappear as they cook. (Of course, it all depends on the ripeness of the pear and how it feels.)
Combine sugar and flour. In large bowl, sprinkle lemon juice over sliced pears (but not strawberries if you add them). Toss with sugar/flour mixture to coat fruit. Fill 9-inch pastry-lined pie plate with pear mixture. Use something deep.
Arrange sliced strawberries over pear filling.
1/2 cup flour
1/2 cup sugar
2 teaspoons ground vanilla bean
1/4 cup butterIn another bowl, combine flour, sugar, and ground vanilla bean. Add butter and toss until mixture resembles coarse crumbs. Sprinkle vanilla mixture evenly over pear filling.
Cover edge of pie with foil. Bake at 375 for 25 minutes. Remove foil from edge of pie and bake an additional 25-30 minutes until pie is bubbly and crust is golden.
Allow to cool completely on wire rack before serving.