Preheat the oven to 175°C.
Melt the butter in a medium nonreactive and oven safe frying pan over medium heat. Add the granola, 1 tablespoon of the flour and 1 tablespoon sugar and toss until the sugar is dissolved and the granola is well-coated. Transfer to a bowl; set aside. (Reserve the pan)
Pour the apples into the frying pan; toss with the pumpkin pie spice, lemon juice and remaining sugar. Cook, stirring occasionally, until the apples are juicy and slightly softened, 5 to 7 minutes. Stir in the remaining 1 tablespoon flour. Scatter the reserved granola mixture evenly over the top and transfer the skillet to the oven. Bake until the crisp is bubbling and the apples are tender, about 35 to 40 minutes. Serve warm.