Background jobs for .NET.
Without the infrastructure.

public class SendWelcomeEmail : IJob<NewUserEvent>
{
    private readonly IEmailService _email;

    public SendWelcomeEmail(IEmailService email)
        => _email = email;

    public async Task ExecuteAsync(
        NewUserEvent payload, JobContext ctx)
    {
        await _email.SendAsync(payload.Email, "Welcome!");
    }
}

public class UsersController(IJobClient jobs)
    : ControllerBase
{
    [HttpPost("register")]
    public async Task<IActionResult> Register(
        RegisterRequest req)
    {
        var user = await CreateUser(req);

        await jobs.EnqueueAsync<SendWelcomeEmail>(
            new NewUserEvent { Email = user.Email });

        return Ok(user);
    }
}