In a medium bowl, combine both flours, salt, sugar and spice blend. Wash your hands, then using your fingertips, rub the butter into the mixture until it is distributed throughout and the mixture is clumpy. (you can also use the food processor but this step is so easy!)
Dump in the rolled oats and again, use your fingers to toss them into the crumble. It will be the consistency of damp sand. Chill the bowl of rye streusel topping while you prepare the apples filling.
Preheat the oven to 375°F. Place rack in the middle of the oven. Lightly coat an 9x9 square baking dish with cooking spray.
In a large bowl, stir together the sour cream, lemon juice and vanilla. Peel, core and finely chop the apples. Using a large spatula, combine the apples with the sour cream until completely coated.
Sprinkle the sugar, flour and cinnamon over the apples. Stir thoroughly to combine and coat the apples.
Scrape the apples and any accumulated juices into the prepared pan. Level the apples in the dish. Using clean hands, sprinkle the chilled rye streusel all over the top. Don't worry if it's not evenly distributed; that's all part of the rustic charm.
Place crisp on the middle shelf in the preheated oven. Check the crisp after about 35 minutes. It should be bubbling in the center and the top a deep brown. Total cooking time could be about 50 minutes, depending on the apples used and if they were room temperature or cold.
Remove apple crisp from oven and cool at least 10 minutes. Enjoy warm, with a scoop of vanilla ice cream.