I am using Azure Key Vault to protect our keys and secrets, but I am unsure how I can use the KeyBundle I retrieve using the .net SDK. How can I create an X509Certificate2 objec
You cannot use the KeyBundle result as an X509Certificate2 object because it simply represents the public key portion of a key pair here (no issuer). See the methods in KeyVaultClientExtensions for functions to encrypt data, verify signatures, etc. using this KeyBundle object.