Preheat the oven to 350 degrees F. Coat a muffin pan with cooking spray.
Place dates in a medium bowl and cover with boiling water. Let soak for 20 minutes. Drain the dates, reserving 1/4 cup soaking liquid. Place half the dates in a food processor (reserve the rest for the filling). Add pecans, oat flour, butter, salt and the reserved soaking liquid; pulse until combined. Firmly press 2 generous tablespoons of the mixture into the bottoms and up the sides of each muffin cup. Bake until set, but not browned, 10 to 12 minutes. Let cool in the pan on a wire rack for 15 minutes.
Meanwhile, place cider and the reserved dates in a blender or food processor; blend until mostly smooth. Transfer to a medium saucepan; add apples and cinnamon. Bring to a simmer over medium-high heat; reduce heat to maintain a simmer and cook, stirring often, until the apples are mostly tender, 12 to 15 minutes. Remove from heat; stir in vanilla and cornstarch.
Using about 2 tablespoons filling for each tart, divide the filling among the crusts. Bake until the crust is browned on the edges and the filling is hot, 12 to 15 minutes. Cool the tarts in the pan on a wire rack for at least 20 minutes. Run a sharp knife around the edges and remove the tarts from the pan.
Serving Size 1
Servings 12
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.