Store the HTML markup in a variable and return it to avoid the text being wrapped in quotes. First store your HTML markup in a variable in the lambda function then return it. For example in Node.js:
context.succeed({ variableHTML: myContentHtml })
Here is an example of the mapping template:
#set($inputRoot = $input.path('$')) $inputRoot.variableHTML .
Here variable HTML contains the HTML markup passed from the lambda function. After that, you needed to create a Response model for HTTP Status, which is accessible through Method Response. Here set the Response model Content-Type as text/html. Then you'll get the HTML page without quotes and the browser recognizes it as HTML.