1Preheat oven to 350. Grease & flour a 9X13 inch pan.
2If using frozen blueberries, thaw out first. Divide berries in half. Mash 1/2,& save rest, unmashed.
3Mix sugar & cornstarch. Add to mashed berries. Cook 5 or 6 minutes on medium heat until thick & clear.
4Add lemon juice and unmashed berries. Mix & cool.
5In large bowl, mix chopped pecans & cake mix.
Melt butter, pour into cake mix & pecans. Mix until all is moistened. Into greased pan, pour undrained pineapple to make an even layer.
Spread berry mixture over pineapple. Do not stir.
6Using hands, sprinkle cake mix mixture over berry mixture, working out lumps in cake mix. Spread evenly.Do not stir.