Monotonous (Adjective) / Monotonously (Adverb)
– lacking in variety; tediously unvarying
-dull, tedious, and repetitious; lacking in variety and interest

Taken from Louise Erdrich’s “The Shawl”

“If she could have thrown off that wrong hearted love, she would have, but the thought of the other man, who lived across the lake, was with her always. She became a gray sky, stared monotonously at the walls, sometimes wept into her hands for hours at a time. “

Erdrich used the word monotonously to show how Aanakwad lacks any interest towards her husband and that she no longer feels like doing anything anymore because she is unhappy as one can be.

source: https://www.merriam-webster.com/dictionary/monotonous