Preheat the oven to 350 degrees F. Grease an 11-by-15-inch baking tray with nonstick cooking spray.
Sift together the flour and baking powder in a large mixing bowl. Combine the carrots, raisins, sugar and condensed milk in a heatproof or glass bowl. Rinse out the condensed milk stuck to the sides of the can using the whole milk, and then add both to the carrots and mix well. Microwave the carrots until soft and have lost their raw texture and taste, 5 to 8 minutes. Stir in the melted butter, nutmeg and cardamom until well combined. (I prefer to add the spices after the carrots are cooked to ensure that the essential oils in the spices do not dissipate.)
Pour the carrot mixture into the center of bowl with the flour. Fold in the carrots gently, working from the sides in towards the center, taking care not to over-mix (this can cause the gluten to bind together, resulting in a tough and leathery texture).
Spread evenly onto the baking tray and sprinkle with the almonds. Bake until the top is golden brown, 20 to 25 minutes. Allow to cool before cutting into squares and serving.
These bars freeze well and will keep up to 1 month in the freezer.