The first
BTC transaction happened on January 12th when Hal Finney received 10
BTC from Satoshi.
More, in 2009 there was the first transaction with an exchange of value, no donation or test, Sirius selling 5050 BTC for 5$.
So, it wasn't really a "first"

Yep! Actually there are 3 different first transaction in bitcoin history.
[1]
Peer to peer transaction which is the 10
BTC sent from satoshi to Hal Finney.
[2]
Crypto to Fiat transaction when Sirius sold an amount of
BTC 5,050 for $ 5.
[3]
Real world transaction is when Laszlo buys 2 pizza for
BTC 10k.