Preheat the oven to 350°F.
In the mixing bowl of a kitchen stand mixer add the olive oil, granulated sugar, eggs and vanilla and mix on low speed with the paddle attachment until well combined.
Sift together the flour, salt, baking soda and cinnamon and slowly mix it into the wet ingredients.
With a spatula, fold in the diced apples and chopped walnuts.
Butter a 9”x13” cake pan and pour the batter in.
Place the cake in the middle of the preheated oven and bake for about 45 minutes or until a toothpick inserted in the center comes out clean.
Remove the cake from the oven and let it cool for about 30 minutes.
In a medium size saucepan, bring the butter, brown sugar and milk to a rolling boil for a full 2 ½ minutes, carefully stirring it so that it doesn’t burn.
Remove it from the heat source and evenly pour it over the top of the whole cake.
Let it cool for 10-15 minutes before serving.
Serve it with a scoop of vanilla ice cream and enjoy!