Preheat oven to 350 degrees F. Butter an 8 by 8 by 2-inch baking pan, and set aside. In a large bowl, combine flour, oats, brown sugar, and baking soda. Add butter, and blend with your fingertips until mixture resembles coarse crumbs. Transfer 2/3 of the crumb mixture into prepared pan, and press into bottom and up sides. Spread date paste over bottom layer of the dough. Cover with remaining crumb mixture. Bake until golden brown, about 35 minutes. Transfer pan to a wire rack to cool completely. Invert onto a plate, then back onto a cutting board. Cut into 2-inch squares. Store in an airtight container for up to 1 week.
Place dates in small saucepan with 1 cup of water, lemon zest, and juice. Cook over medium heat until soft, about 12 minutes. Remove from heat, cool completely before using.
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