The rainbow means he/she is at peace. That much is obvious. (You already knew that, though).

It also means "thank you and blessings" from your friend. Your soul-mate is thankful for the time with you. (The message is a gift...it is not easy to cross the divide to leave a gift...it requires MUCH effort...a sign of how important you are to them)

As for the oven...some clues that your friend sends...only YOU will know if they have meaning. If you understand the connection, then it was your friend. If you see no connection, then it was coincidence.

If they have a message to send, there will be very little question left in your mind. They will send it in a way you can understand it for what it is.