The eating in Windermere splits roughly into three: the family-pub-and-fish-and-chips circuit in Bowness, a quieter set of more ambitious restaurants up the hill in Windermere town, and a handful of country-house and gastro options spread out around the edge of the lake.
In Bowness, The Angel Inn does a good upmarket pub menu with proper Cumbrian sourcing; Lucy's on a Plate in Ambleside (sister restaurant) is reliable for breakfast and lunch. In Windermere, Hooked is the best fish restaurant in the area, and Francine's does straightforward bistro cooking that has been keeping return visitors happy for years. For a special meal, Holbeck Ghyll above Windermere has a Michelin-starred restaurant in a country-house hotel with stunning lake views, and Linthwaite House offers similar in a more contemporary setting.
For something quick, the bakeries on Crescent Road in Windermere town make decent sandwiches; Poppi Red in Bowness is a much-loved café for cake and a pot of tea.