Expression for counting features that intersect other layer in QGIS

Question

I'm working with QGIS 3.16 Hannover.

I've got a single polygon layer National Park and another layer with a 1x1 km grid UTM. In the print composer, I want to include in the legend the number of UTM grid squares that intersect the National Park (all features of UTM with all features of National Park, so I get one number as result). I've built the following code, but it returns 0.

aggregate(
          layer:='UTM', 
          aggregate:='count', 
          expression:='COD1X1', 
          filter:=intersects($geometry, geometry('National Park') 
                            ) 
          )

What's wrong?

Answer 1

To get the count of all UTM-features that intersect with the current National Park feature:

aggregate(
          layer:='UTM', 
          aggregate:='count', 
          expression:='COD1X1', 
          filter:=intersects($geometry,geometry(@parent)) 
)

To count all UTM-Features that intersect with all National Park features:

aggregate(
          layer:='UTM', 
          aggregate:='count', 
          expression:='COD1X1', 
          filter:=intersects($geometry,aggregate('National Park','collect',$geometry)) 
)