Preheat oven to 300°. Line the bottom of a 10-inch springform pan or a 13x9-inch baking pan with parchment paper, then grease the parchment.

Whisk together the flour, baking soda, salt, cinnamon, nutmeg, ginger, cloves, and the rolled oats in a large mixing bowl.

In a separate mixing bowl beat the oil, sugar, and eggs until they're slightly thick, about 2 minutes. Stir in the vanilla and lemon juice.

Add the dry ingredients to the wet mixture, stirring just until moistened. Fold in the chopped apples and optional walnuts. The batter will be thick.

Transfer the batter to the prepared pan. Bake until a toothpick inserted in the center comes out clean, about 55–60 minutes. Cool the cake in the pan on a rack.