Why are my bitcoin transactions going to 2 addresses Here is my transaction:
https://blockchain.info/tx/3ddd5a173a73fc82bb0e1eb4361b8c36eb65919e2bfb9ee78fe2c6b5ff3f2307

I only sent .003 BTC to 1 address (35iR3hnFqmkHswRm8PmZgTKxYm7GfucNZJ), but the transaction shows BTC being sent to 2 addresses. This is exactly what happened to me one month ago with another transaction:
https://blockchain.info/tx/672744cd9a355b908fbf256680726e96279c13a8c39770a30a472c25371c6798

Since you guys tend to be pretty cynical (meaning you're smart) I have attached a screenshot as proof that I did not try to send the transaction to 2 addresses.
When you have to pay a transction from an address that is only part of the total balance of that address the program you use for managing your wallet (in your case bitcoin core) sends to the destination the amount that you wanted (in your case 0.003), and the rest is sent back to another address of your own (minus the fee).

This is because for how transactions are designed in bitcoin when you make an outgoing transaction from an address you cannot use just a part of it. All of it must be spent in transaction (towards 1 or more addresses) and the rest goes to the miner as a fee.