Final answer:
The main idea of the social media message is conveyed in the call to action, which is to try the raspberry and chocolate cupcakes.
Step-by-step explanation:
The sentence in the social media message that shows the main idea is 'Try our raspberry and chocolate cupcakes.' This is the sentence where the call to action is made, and it sets the stage for the description that follows. While other sentences provide supporting details, such as the special raspberry cream filling being heavenly and the encouragement to not take the company's word for it, it's the initial suggestion to try the cupcakes that represents the central message of the social media post.
It emphasizes the appeal and quality of the cupcakes.