eigen3 error with ros foxy

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I am trying to build a package, within a docker file, and it throws this error

CMake Error at /opt/ros/foxy/share/ament_cmake_target_dependencies/cmake/ament_target_dependencies.cmake:66 (message):   ament_target_dependencies() the passed package name 'Eigen3::Eigen' was not   found before   Call Stack (most recent call first):   CMakeLists.txt:82 (ament_target_dependencies)

now i have installed libeigen

libeigen3-dev is already the newest version (3.3.7-2).

and foxy eigen 3 cmake module

ros-foxy-eigen3-cmake-module is already the newest version (0.1.1-1focal.20210423.000604).

what am i missing here?