Note: I always use real butter but was out today and found this stick of margarine. My recommendation is real butter (always better for you than margarine). If you don't want to use that much butter, use half butter and half coconut oil.
1 box sugar-free yellow cake mix (2 layer size)
1 can pineapple* in juice (no syrup)
1 stick butter (see note above)
Preheat oven to 350 degrees.
Lightly butter a 9" X 13" baking pan.
Spread the pineapple with juice over the bottom of the pan.
Sprinkle the dry cake mix over the pineapple, evening out to equally cover the pineapple.
Melt the butter and drizzle overall.
Bake at 350 degrees 35-40 minutes or until lightly browned.
Serve topped with whipped cream.
Note: This is a dessert not a cake. You cannot 'frost' this dessert.
*I just happened to have chunked pineapple on hand. It worked out fine but next time just to see the difference I will try crushed pineapple. I will also sprinkle with some chopped pecans next time. I didn't think about them today.