Preheat oven to 350 degrees F (175 degrees C). Grease and flour one 9x13 inch cake pan.
In a mixing bowl; beat oil and eggs with an electric mixer until creamy. Add the sugar and vanilla and beat well.
Combine the flour salt, baking soda, and ground cinnamon together in a bowl. Slowly add this mixture to the egg mixture and mix until combined. The batter will be very thick. Fold in the apples by hand using a wooden spoon. Spread batter into the prepared pan.
Bake at 350 degrees F (175 degrees C) for 45 minutes or until cake tests done. Let cake cool on a wire rack. Once cake is cool serve with a dusting of confectioners' sugar or with a Cream Cheese Frosting.
Managing the Heavy Batter
Folding four cups of diced fruit into a minimal amount of flour mixture requires a deliberate hand to prevent gluten overdevelopment. Mix the oil and eggs thoroughly with an electric appliance until emulsified before introducing dry components, because this initial aeration provides the primary lift for a dense crumb. Incorporate the flour gradually to avoid pocketing pockets of unhydrated dry matter, keeping in mind that the resulting mixture will appear exceptionally stiff before the fruit is added.
Fruit Selection and Moisture
Fresh fruit introduces significant water content during baking, whereas dehydrated or canned alternatives alter both the structural integrity and baking time of the finished dessert. Peel and core firm cultivars like Granny Smith or Honeycrisp uniformly to ensure they soften at an identical rate within the crumb structure. Dice the pieces evenly so they distribute throughout the heavy batter without sinking entirely to the bottom of the 9x13 inch pan.
Baking and Cooling Protocols
Set the oven accurately to 350 degrees Fahrenheit and monitor the bake closely around the 45-minute mark. Insert a wooden skewer into the center of the cake; it should emerge clean without wet batter clinging to it. Allow the pan to rest completely on a wire rack to stabilize the crumb structure before attempting any dusting of confectioners' sugar or applying a rich cream cheese frosting.