Preheat the oven to 350°F. Line an 8 × 8-inch baking dish with parchment paper, leaving about 2 inches of extra parchment over both sides.

In a small saucepan, bring 11/4 cups of water to a boil over high heat. Add the dates and boil, stirring occasionally, until the liquid has evaporated and the dates have melted and thickened, about 5 minutes. Remove the pan from the heat; stir in the lemon juice and pecans. Set aside to cool for 10 minutes.

In a large bowl, whisk the flour, oats, sugar, cinnamon, baking soda, and salt. Pour the melted butter on top. Using your fingertips, rub the butter into the flour mixture until you have a pebbly texture with moist pea-size clumps.

Press half of the flour mixture evenly and firmly over the bottom of the prepared baking dish. Spread the date mixture evenly over the top. Sprinkle the remaining flour mixture over the date mixture; press gently to help the crumbs adhere.

Bake until the top and edges are golden brown, 35 to 40 minutes. Transfer the baking dish to a wire rack and cool completely. Cut into 16 bars and serve.