Make a plane at 45degrees to the top of the plate.
Draw your circle on the plane and extrude it through the plate.
This is 1 of MANY poosible ways to do the job.
If you want you can actually show the tube and extrude it as a multibody. Then convert the outside edge and extrude- cut through the plate body only.
Then you can suppress or hide either body to show which you want to be seen.
You can also select the multibodies and save them as individual components.
Works almost like an assembly only without mates and all that crap.
On a personal note I tend to use multibody parts in a lot of cases that could only be done as a much more complicated assembly in the past.