How to Make It
Prepare the filling: Place dates in a small bowl; add hot water to cover. Let stand until softened, about 30 minutes; drain.
Place drained dates, 1 teaspoon vanilla, 1 teaspoon cinnamon, and 1/8 teaspoon salt in a food processor. With processor running, add 1/4 cup orange juice, 1 tablespoon at a time, until smooth.
Prepare the cake: Preheat oven to 350°F. Stir together flour, baking powder, baking soda, 1/2 teaspoon cinnamon, cardamom, and 1/4 teaspoon salt in a medium bowl.
Stir together 2/3 cup yogurt, brown sugar, oil, eggs, 1 tablespoon zest, 1/2 cup juice, and 1 teaspoon vanilla in a separate bowl. Stir yogurt mixture into flour mixture.
Coat a 12-cup Bundt pan with cooking spray. Set aside 1 1/2 cups batter. Pour remaining batter into prepared pan. Spoon filling over batter; use the back of a spoon to spread evenly. Sprinkle walnuts over date mixture. Pour 1 1/2 cups reserved batter over walnuts. Bake at 350°F until a wooden pick inserted in center comes out clean, about 30 minutes. Cool in pan on a wire rack 10 minutes; invert cake onto rack, and cool completely.
Prepare the glaze: Whisk together 1/4 cup yogurt, powdered sugar, 1/2 teaspoon zest, and 1 tablespoon juice in a medium bowl. Spread glaze over cake.