Preheat your oven to 350°F (175°C). Grease and flour a 9-inch square cake pan or line it with parchment paper.

In a large mixing bowl, sift together the all-purpose flour, baking powder, baking soda, cinnamon, nutmeg, mixed spice, and salt. Set aside.

In another bowl, whisk the beaten eggs, granulated sugar, brown sugar, vegetable oil, and vanilla extract until smooth and well combined.

Gradually add the dry ingredients into the wet mixture, folding gently to combine without over mixing.

Fold in the finely grated carrots, drained crushed pineapple, and if using, the chopped walnuts or pecans and raisins. Mix just until evenly distributed.

Transfer the batter to the prepared cake pan, smoothing the top with a spatula.

Place the pan in the oven and bake for 40 to 45 minutes, or until a toothpick inserted into the center comes out clean.

Remove the cake from the oven and allow it to cool in the pan for about 10 minutes before transferring to a wire rack to cool completely. Serve plain or with cream cheese frosting if desired.