For the topping
1 oz. (1/4 cup) unbleached all-purpose flour
1/4 cup packed brown sugar (preferably dark)
1/4 cup old-fashioned oats
1/8 tsp. table salt
2 oz. (4 Tbs.) cold unsalted butter, cut into 1/2-inch cubes
3/4 cup pecans, toasted and coarsely chopped

For the filling
1 oz. (2 Tbs.) unsalted butter
1/2 cup packed brown sugar (preferably dark)
1/4 cup fresh orange juice (from 1 medium orange), strained
1 tsp. ground cinnamon
1/8 tsp. table salt
6 medium ripe bananas (about 2 lb.), peeled, halved crosswise, and then halved lengthwise

Lightly sweetened whipped cream or vanilla ice cream, for serving