My husband who is Polish says obiad should be dinner and kolacja should be supper. There is no lunch.
Polish dinner, or obiad, falls between 2-3pm when most people get home work. It typically is the largest meal of the day. Kolacja is usually a small meal around 7pm.
It should be pointed out that in the last two of these examples, the accusatives (ciastko, tort) are the same as the nominatives, so they're not very helpful to people trying to familiarize themselves with the idea of the accusative! :)
In the second case, you've chosen a noun that does change in the accusative (banan -> banana), but an English speaker is likely to think 'banana' is the nominative. Confusing :)