Preheat the oven to 350°F (180°C).
Grease a 9-inch (white ceramic) square baking pan with vegetable oil and line with parchment paper.
In a large bowl, stir together the flour, sugar, baking soda, salt, and cinnamon.
In a medium bowl, whisk together the jam, water, oil, vinegar, and vanilla.
Using a spatula, stir the wet mixture into the dry mixture. Before they are completely mixed, add the walnuts, carrots and prunes, and stir until you see no more lumps of flour.
Transfer to the prepared baking pan and bake for approx 1hr 20 min or until internal temp is between 208 - 210 in the center.
Let the cake cool in the pan for 15 minutes, then transfer it to a rack to finish cooling.
Sprinkle with confectioner's sugar before serving.