Step 1

Preheat the oven to 375 degrees F.

Step 2

Grease a 9-by-13-inch glass or light-colored metal baking pan with butter and sprinkle about 1/3 of a cup of cinnamon sugar at the bottom.

Step 3

Move the pan around so that cinnamon sugar sticks to where the butter was…which should be everywhere in the pan.

Step 4

Discard any cinnamon sugar that did not stick to the butter.

Step 5

Set aside.

Step 6

Bring the water to a boil.

Step 7

Place the butterscotch chips in a small bowl and toss them with the 2 TBSP of flour. This will keep them from settling at the bottom during baking. Set aside.

Step 8

Place the oats and butter cubes in a large bowl.

Step 9

Pour the boiling water over the oat mixture, wait 30 seconds, and stir to moisten all the oats and melt the butter.

Step 10

Let the oat mixtures set for 25 to 30 minutes.

Step 11

In a separate large bowl, whisk together the eggs, vanilla extract, both sugars, salt, baking soda, baking powder, cream of tartar, and cinnamon until combined.

Step 12

Fold in the cooled oatmeal and stir until well combined.

Step 13

Gently fold in the remaining flour and then the butterscotch chips.

Step 14

Pour the batter into the prepared pan.

Step 15

Sprinkle remaining cinnamon sugar on top of batter.

Step 16

Bake the cake for 35-40 minutes, or until a toothpick inserted in the center comes out clean. Let the cake cool on a wire rack until completely cooled.

Step 17

While the cake is cooling make the cream cheese frosting.

Step 18

In the bowl of a standing mixer fitted with the paddle attachment, beat the butter until it is completely smooth.

Step 19

Add the cream cheese and beat until combined.

Step 20

Add the powdered sugar, cinnamon sugar, and vanilla and beat until smooth, about 1 minute.

Step 21

Frost the cooled the cake with cream cheese frosting. Cut into pieces and serve.

Step 22

Note-The frosted cake can be kept refrigerated and tightly covered, for up to 3 days.