Preheat the oven to 350 F (180 C) from up and down. Place the oven rack in the middle of the oven.
In an electric stand mixer fitted with a paddle attachment, place the olive oil, melted butter, and sugar. Mix on medium speed for 5 minutes.
Add the eggs and vanilla, and mix on medium until mixture is creamy and fluffy, 1-2 minutes.
Place a sifter over a large bowl, and sift together the flours, baking soda, cinnamon, salt, and cardamom powder, and whisk to combine. Add this mixture to the wet batter, and use a rubber spatula to just combine.
Add the chopped apples, dates, and walnuts, and fold until just combined. It'll be a thick, chunky batter. Prepare a bundt cake pan by thoroughly greasing softened butter and then dusting evenly with sugar until every crack in the pan is well coated. Pour the batter in the prepared pan, then place in the oven and cook for 55-60 minutes or until toothpick inserted in the center of the pan comes back clean.
Let the cake cool 15-20 minutes, then gently run a butter knife around the edges and center of the cake to loosen it from the bundt cake pan, then invert onto serving plate. Leave it like this for 10 minutes, then gently tap the top of the bundt cake pan, and slide it off the top. Cool a little more before slicing and enjoying!