Take the meatballs out of the refrigerator about 10 minutes ahead of time. Place the baguette on a cutting board. Slice the baguette in half lengthwise.

Spread the tomato sauce on the bread, then place the meatballs on top. Close the sandwich with the other half of the bread.

Place the sandwich on a plate and cover with a microwave-safe lid. Microwave at high power for 2-3 minutes. Remove the sandwich from the microwave.

Let the sandwich cool slightly, then cut it in half. Place the sandwich on a plate to serve.