With cake you connect to an electrum server, and the app scans the chain for sp payments. It takes a while, ~120000 blocks to scan through.
I thought that too, but then I found that cake has a fork of electrs that provides a silent payment tweak endpoint
https://github.com/cake-tech/blockstream-electrs/tree/cake-update-v1
https://github.com/cake-tech/blockstream-electrs/tree/cake-update-v1