For the Topping

1. In a bowl, blend together, using your fingers if easiest, all of the ingredients, mixing together until they become a fine crumble.
2. Place it in the fridge to set until ready to use.

For the Cake

1. Preheat oven to 350 degrees.
2. In a 10-inch cast iron skillet over medium high heat, melt the butter.
3. Once the butter is melted and beginning to bubble, lay the pineapple rings in a single layer in the skillet and allow them to begin to caramelize, about 2 minutes per side, turning over and ensuring that both sides are caramelizing.
4. Remove them from the skillet, and set aside until ready to use.
5. In a large bowl, whisk together the flour, sugar, baking powder and salt.
6. Utilizing a hand held mixer, mix together the milk, butter and vanilla into the flour mixture.
7. With the mixer on low speed, add in one egg yolk at a time, ensuring it is evenly mixed in before adding the next.
8. Spread the batter into the cast iron skillet. Top the batter with the caramelized pineapple slices.
9. Then lastly add in the cooled crumble topping that you created in the first step.
10. Bake the cake for about 35 minutes, and allow to cool on a wire rack.

For the Glaze

1. In a small saucepan, combine all the ingredients and bring to a simmer, stirring frequently until syrupy and smooth.
2. Pour it over the cake prior to serving.