Preheat oven to 350°F (175°C) and grease a 9-inch round cake pan or line with parchment paper.
In a large bowl, whisk together flour, baking powder, cinnamon, and a pinch of salt.
In another bowl, beat together sugar, vegetable oil, and eggs until smooth.
Fold in grated carrots (and optional nuts or raisins).
Gradually mix dry ingredients into the wet mixture until just combined.
Pour batter into the prepared cake pan and smooth the top.
Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
Cool in the pan for 10 minutes, then transfer to a wire rack.
Optional: Frost with cream cheese frosting once the cake has completely cooled.