Pineapple Upside Down Cake

I made a pineapple upside down cake using a recipe from Vegweb.  It was super quick, it literally took under 10 minutes from starting it to putting it in the oven, but I had some issues with the baking.  I took it out of the oven after 25 minutes when it looked perfectly golden brown, but when I inverted it on a plate it was completely uncooked inside so it went back in the oven for probably about another 20 or so minutes.  When I then read through the comments on the recipe it seems like a few other people had the same issue, not sure why?

Ingredients

•     1 1/2 cups plain flour
•     1 cup sugar (I would only use half a cup next time because it is a very sweet cake)
•     1 teaspoon baking soda
•     1/2 teaspoon salt
•     1 cup pineapple juice/water (see below)
•     1/3 cup oil (I used canola oil)
•     1 tablespoon white vinegar (I used apple cider vinegar)
•     1 can pineapple slices in unsweetened pineapple juice
•     1/4 cup UNPACKED brown sugar (I would leave this out next time as it didn't caramelise like I   thought it would so seemed a bit unneccesary)

Directions:

• Preheat oven to 180 degrees.
• Mix flour, sugar, baking soda, and salt in a large bowl.
• Pour juice off can of pineapple into 1 cup measuring cup--it should be about 3/4 cup juice.   Add water to make 1 cup.  In a separate bowl, combine oil, vinegar and juice.
• Place pineapple slices into the bottom of a 12 inch spring form pan.   Sprinkle with brown sugar.
• Quickly mix wet ingredients into dry, stirring quickly to combine ingredients well and get out the big lumps.  Pour into pan on top of the pineapple/brown sugar mix.
• Bake for 25-35 minutes or until golden on top and a toothpick inserted in the center comes out clean. 
• Let cool and loosen sides of cake from pan.  Remove side ring and place serving plate on top.   Flip cake over onto serving plate and remove pan bottom.