Tomatoes were absent from early lasagna because Christopher Columbus reached the Americas in 1492.
Tomatoes are native to the Americas, with their early history tied especially to cultivation in Mesoamerica and South America. Columbus’s first voyage, beginning in 1492, initiated the sustained Columbian exchange between the Americas and Europe. That exchange eventually carried American crops—including tomatoes, maize, potatoes, peppers, and cacao—into European agriculture and cuisine.
This explains why medieval and early Renaissance lasagna recipes contain no tomato sauce. The Liber de Coquina recipe, written centuries before Columbus’s voyage, uses pasta sheets, cheese, and spices instead. The absence is chronological rather than evidence that cooks had rejected tomatoes.
Tomatoes did not instantly become a staple after 1492. The earliest known European literary discussion appeared in Pietro Andrea Mattioli’s 1544 herbal, and tomatoes were initially grown in Italy largely as ornamental plants. Their culinary use expanded gradually, with tomato-based Italian cooking becoming especially important in later centuries. The first discovered cookbook with tomato recipes was published in Naples in 1692.