Can a Circle of the Stars druid fire an arrow from its star form and cast a spell of 1st level or higher during the same turn?

The druid subclass Circle of the Stars from Unearthed Arcana: Subclasses, Part 3 has the 2nd-level feature Starry Form, part of the description of which states:

You gain a bonus action that you can use to make a ranged spell attack, hurling a luminous arrow that targets a creature you can see within 60 feet of you. On a hit, the attack deals radiant damage equal to 1d8 + your Wisdom modifier.

Does “making a ranged spell attack” count as casting a spell and therefore limit your action to a cantrip or can you cast a spell of first level or higher because the arrow is not a spell? Could I cast one of the freely available Guiding Bolts and fire an arrow or do I have to stick with something like frostbite and an arrow?