I need to attach 3/4” engineered flooring to stair tread at top of landing. The tread is 2”Doug fir. What is best approach? I am thinking of routing a groove into the tread and gluing a spine in place and gluing first piece of flooring to the spline. Will the spline make the connection stronger? Any comments or recommendations will be much appreciated.

Making a groove and using a spline to glue everything together is good. Also, glue the flooring to the sub-floor near the nosing.