This solution has been tested on your sample HTML page. You will have to craft the CSS selector to be specific enough on the actual page. And/or filter the resulting elementHandles:

const puppeteer = require('puppeteer');

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto('https://renatocfrancisco.github.io/getTableWithPuppeteer/');

  // Get array of elementHandles from page matching this CSS selector.
  const elements = await page.$$('table table td');

  const columns = [];
  const values  = [];

  // Process the elementHandles.
  let i = 0;
  for (const element of elements) {
    // Extract text from elementHandle.
    const text = await element.evaluate(el => el.textContent);
    if ((i++ % 2) == 0) {
        // Even elements are columns.
        columns.push(text);
    } else {
        // Odd elements are values.
        values.push(text);
    }
  };

  // Construct CSV string.
  console.log(`${columns.join(',')}\n${values.join(',')}`);

  await browser.close();
})();

Output:

$ node ./src/index.js 
column1,column2,column3
value1,value2,value3

update:

This is a variation that doesn't use Puppeteer; only fetch and Cheerio.js. It is much faster and uses less resources, so I recommend using this version when possible. (Your sample URL can be processed fine without Puppeteer.)

const cheerio = require('cheerio');

(async () => {
  const fetch = (...args) => import('node-fetch').then(({default: fetch}) => fetch(...args));
  const response = await fetch('https://renatocfrancisco.github.io/getTableWithPuppeteer/');
  const html = await response.text();
  const $ = cheerio.load(html);

  // Get array of elements from page matching this CSS selector.
  const elements = $('table table td');

  const columns = [];
  const values  = [];

  // Process the elementHandles.
  let i = 0;
  for (const element of elements) {
    // Extract text from elementHandle.
    const text = $(element).text();
    if ((i++ % 2) == 0) {
        // Even elements are columns.
        columns.push(text);
    } else {
        // Odd elements are values.
        values.push(text);
    }
  };

  // Construct CSV string.
  console.log(`${columns.join(',')}\n${values.join(',')}`);
})();

Output:

$ node ./src/index.js 
column1,column2,column3
value1,value2,value3

This is a little cumbersome as I have broken down the steps to illustrate what we are doing. It could be simplified greatly if the relevant tbody had an ID so we could make a direct reference to it using getElementById but instead we have to navigate the DOM tree (the relevant table is inside a cell of an outer table).

Having made a reference to a collection of relevant table rows, we can loop though them to extract the data needed. The loops build a comma-separated string for each (output) row, storing them in an array. The array is later joined into lines to give csv output.

This could undoubtedly be simplified but it works. Snippet:

const innerTable = document.getElementsByTagName('table')[1];

const tableBody = innerTable.getElementsByTagName('tbody')[0];

const tableRows = tableBody.children;

let csv = [];

for (let row=0; row<tableRows.length; row++) { 
  const cells = tableRows[row].children;
    for (let cell=0; cell<cells.length; cell++) {
      if (csv[cell]) {csv[cell] += `,${cells[cell].innerText}`;}
      else {csv[cell] = `${cells[cell].innerText}`;}
      
    } // next cell;
    
} // next row;

csvString = csv.join("\n");
console.log(csvString);

<table style="color:Black;background-color:LightGrey;height:400px;width:898px;border: 1px solid grey">
        <tbody>
            <tr>
                <td>
                    <table>
                        <tbody>
                            <tr>
                                <td>Column1</td>
                                <td>Value1</td>
                            </tr>
                            <tr>
                                <td>Column2</td>
                                <td>Value2</td>
                            </tr>
                            <tr>
                                <td>Column3</td>
                                <td>Value3</td>
                            </tr>
                        </tbody>
                    </table>
                </td>
            </tr>
        </tbody>
    </table>