<div class="container">
  <p class="column">1</p>
  <p class="column">2</p>
  <p class="column heading">Heading</p>    
</div>
.container {
  display: grid;
  grid-template: 
    "heading heading" auto
    "one two" auto
    / 
    2fr 1fr;
  /* Shorthand for:   
  grid-template-rows: auto auto;    
  grid-template-columns: 2fr 1fr;  
  grid-template-areas: 
    "heading heading"
    "one two";   
  */  
  gap: 10px;
}

.column.heading {
  grid-area: heading;
  border-color: black;
}

/* etc: */

body {
  margin: 1.5em;
  font-size: 130%;
}

.column {
  background: #b3e888;
  padding: 1em;
  margin-top: 0;
  margin-bottom: 0;
  font-family: monospace;
  text-align: center;
  border: 1px solid darkgreen;
  /* "border-collapse" hack */
  margin-left: -1px;
  margin-top: -1px;
}

.container {
  border: 5px solid black;
  padding: 1em;
  margin-bottom: 2em;  
}

External CSS

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External JavaScript

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