Preheat the oven to 350 F (180 C) and line a muffin tray with 18 liners
Prepare the apples and sprinkle cubes with a bit of lemon juice to keep from browning
In a medium sized bowl, whisk together the eggs, sugar, oil and vanilla
Add in the cinnamon, soda and salt, whisk again to incorporate
Blend in a cup of flour at a time, switch to a spoon or spatula to make it easier to stir. The batter will be quite thick
Fold in the apple chunks so that they are well-distributed through out the batter
Using an ice cream scoop (or spoon), fill the liners 3/4 of the way full with batter
Sprinkle tops with around 1-2 tsp of brown sugar, and pop into the oven
Bake for 20-24 min or until a toothpick comes out clean, and serve warm or at room temperature