Just use a list comprehension:
nested_lst_of_tuples = [tuple(l) for l in nested_lst]
Demo:
>>> nested_lst = [['tom', 'cat'], ['jerry', 'mouse'], ['spark', 'dog']]
>>> [tuple(l) for l in nested_lst]
[('tom', 'cat'), ('jerry', 'mouse'), ('spark', 'dog')]
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